A332986 Successive differences of index of triangular numbers sum of two pentagonal numbers.

1, 4, 6, 18, 2, 7, 1, 4, 1, 2, 4, 5, 5, 3, 1, 2, 2, 5, 3, 3, 4, 3, 1, 10, 1, 1, 8, 3, 4, 7, 5, 12, 10, 8, 9, 7, 3, 5, 3, 6, 3, 10, 11, 1, 2, 13, 9, 6, 3, 2, 1, 2, 3, 3, 2, 2, 6, 13, 9, 4, 1, 11, 1, 3, 8, 9, 1, 4, 6, 3, 8, 3, 5, 2, 3, 2, 5, 1, 14, 9

Offset

1,2

Comments

The behavior of this sequence is unexpectedly quite complex.

Links

Peter Kagey, Table of n, a(n) for n = 1..2500

Crossrefs

Cf. A000217 (triangular numbers), A000326 (pentagonal numbers), A332987 (sums of two nonzero pentagonal numbers), A333009 (analog for indices of square numbers).

Cf. First differences of A332985.

Sequence in context: A211949 A079803 A061361 * A113610 A309334 A263319

Adjacent sequences: A332983 A332984 A332985 * A332987 A332988 A332989

Keyword

nonn

Author

Olivier Gérard, Mar 05 2020

Status

approved