A249622 a(n) = number of ways to express A117048(n) as the sum of two positive triangular numbers.

1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 3, 2, 1, 1, 3, 1, 2, 1, 1, 2, 1, 3, 1, 2, 1, 2, 1, 1, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 4, 1, 3, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 2, 4, 1, 1, 1, 3, 1, 1, 2, 1, 2, 2, 1, 1, 2, 1, 1, 3, 1, 2, 1, 2, 1, 1, 6, 2, 1, 1, 1, 1

Offset

1,6

Links

Zak Seidov, Table of n, a(n) for n = 1..10000

Example

a(6) = 2 because A117048(6) = 31 and 31 = 3 + 28 = 10 + 21 (first case of two-way expression).
a(22) = 3 because A117048(22) = 181 and 181 = A000217(i) + A000217(k), for {i,k} = {{4, 18}, {7, 17}, {9, 16}} (first case of three-way expression): 181 = 10 + 171 = 28 + 153 = 45 + 136.

Crossrefs

Cf. A000040, A000217, A002383.

Sequence in context: A043287 A212177 A345999 * A287656 A043286 A172098

Adjacent sequences: A249619 A249620 A249621 * A249623 A249624 A249625

Keyword

nonn

Author

Zak Seidov, Nov 03 2014

Status

approved