Perrin numbers (#24)

VascoSch92 · Jan 6, 2024 · c7e4602 · c7e4602
2 parents c3ee435 + 79544f2
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -25,6 +25,7 @@ The version is represented by three digits: a.b.c.
 ENHANCEMENT:
 - sequentium.github.workflows.release.yml: workflow for automatic upload on pypi
 - sequentium.sequence.sequences.integer.periodic_generalised.py: added class for representing constant sequences
+- sequentium.sequence.sequences.integer.recursive.py: added sequence A001608
 
 ---
 ## [0.0.1] - 2024-01-02

diff --git a/sequence/SEQUENCES_LIST.md b/sequence/SEQUENCES_LIST.md
@@ -29,6 +29,7 @@ List of implemented integer sequences.
 | A001228 | Orders of sporadic simple groups | `A001228`                                                 | https://oeis.org/A001228                         |
 | A001591 | The Pentanacci numbers           | `A001591`, `PentanacciNumbers`                            | https://oeis.org/A001591                         |
 | A001592 | The Hexanacci numbers            | `A001592`, `HexanacciNumbers`                             | https://oeis.org/A001592                         |
+| A001608 | Perrin numbers                   | `A001608`, `PerrinNumbers`                                | https://oeis.org/A002203                         |
 | A002203 | Companion Pell numbers           | `A002203`, `CompanionPellNumbers`, `PellLucasNumbers`     | https://oeis.org/A002203                         |
 | A002808 | The composite numbers            | `A002808`, `CompositeNumbers`, `PositiveCompositeNumbers` | https://oeis.org/A002808                         |
 | A003173 | The Heegner numbers              | `A003173`, `HeegnerNumbers`                               | https://oeis.org/A003173                         |

diff --git a/sequence/sequences/integer/recursive.py b/sequence/sequences/integer/recursive.py
@@ -108,6 +108,20 @@ def __init__(self) -> None:
 HexanacciNumbers = A001591
 
 
+class A001608(AlmostMonotonicIncreasingMixin, Recursive):
+    """Perrin numbers (https://oeis.org/A001608)."""
+    sequence_name = 'Perrin numbers'
+    offset: ClassVar[List[int]] = [3, 0, 2, 3, 2, 5]
+
+    def __init__(self) -> None:
+        super().__init__(start_terms=(3, 0, 2))
+
+    def formula(self, terms: Tuple[Any, ...]) -> Tuple[Any, ...]:
+        return terms[1], terms[2], terms[1] + terms[0]
+
+
+PerrinNumbers = A001608
+
 class A002203(LucasSequenceV):
     """Companion Pell numbers (https://oeis.org/A002203)."""
     sequence_name = 'Companion Pell numbers'

diff --git a/tests/tests_integer_sequences/test_recursive.py b/tests/tests_integer_sequences/test_recursive.py
@@ -82,6 +82,16 @@ class TestA001592(SequenceTestSuite):
     ]
 
 
+class TestA001608(SequenceTestSuite):
+    sequence = A001608()
+    sequence_name = 'Perrin numbers'
+    ground_truth = [
+        3, 0, 2, 3, 2, 5, 5, 7, 10, 12, 17, 22, 29, 39, 51, 68, 90, 119, 158, 209, 277, 367, 486, 644, 853, 1130, 1497,
+        1983, 2627, 3480, 4610, 6107, 8090, 10717, 14197, 18807, 24914, 33004, 43721, 57918, 76725, 101639, 134643,
+        178364, 236282, 313007,
+    ]
+
+
 class TestA002203(SequenceTestSuite):
     sequence = A002203()
     sequence_name = 'Companion Pell numbers'