A255261 a(n) = a(n-1) + sum of the hexagonal numbers which are among the first (n-1) terms of the sequence, with a(1)=1.

1, 2, 3, 4, 5, 6, 13, 20, 27, 34, 41, 48, 55, 62, 69, 76, 83, 90, 97, 104, 111, 118, 125, 132, 139, 146, 153, 313, 473, 633, 793, 953, 1113, 1273, 1433, 1593, 1753, 1913, 2073, 2233, 2393, 2553, 2713, 2873, 3033, 3193, 3353, 3513, 3673, 3833, 3993, 4153

Offset

1,2

Links

Colin Barker, Table of n, a(n) for n = 1..1000

Example

a(8) = 20 because a(7) = 13, hexagonal numbers already in the sequence are 1 and 6, and 13+1+6 = 20.

Prog

(PARI) vector(100, n, if(n==1, a_n_1=sum_=1, a_n_1+=sum_; if(ispolygonal(a_n_1, 6), sum_+=a_n_1)); a_n_1)

Crossrefs

Cf. A100963, A101135, A255260.

Sequence in context: A057224 A153695 A300857 * A181303 A276529 A200330

Adjacent sequences: A255258 A255259 A255260 * A255262 A255263 A255264

Keyword

nonn

Author

Colin Barker, Feb 20 2015

Status

approved