1,2

The behavior of this sequence is unexpectedly quite complex.

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

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

nonn

Olivier Gérard, Mar 05 2020

approved