A059406 a(n) = a(n-1)*(3a(n-1) + 1)/2 with a(1) = 1.

1, 2, 7, 77, 8932, 119675402, 21483302825630107, 692298450446589820159203790062227, 718915716736124071145150312487360788973317227637596552328693330407

Offset

1,2

Comments

a(1) = 1, a(n+1) = sum of a(n) numbers beginning with a(n) + 1: a(2) = 2, a(3) = 3+4 = 7, a(4) = 8+9+...13+14 = 77. - Amarnath Murthy, Sep 07 2005

Links

Harry J. Smith, Table of n, a(n) for n = 1..12

Formula

a(n) = A007501(n)/3 = A005449(a(n-1)). - Henry Bottomley, Oct 03 2001

Example

a(3) = 7 so a(4) = 7*(3*7 + 1)/2 = 7*22/2 = 77.

Mathematica

f[n_Integer] := n(3n + 1)/2; NestList[f, 2, 8]

Prog

(PARI) { a=2/3; for (n = 1, 12, write("b059406.txt", n, " ", a=a*(3*a + 1)/2); ) } \\ Harry J. Smith, Jun 26 2009

Crossrefs

Cf. A000326.

Sequence in context: A083829 A067963 A304980 * A042791 A128293 A354426

Adjacent sequences: A059403 A059404 A059405 * A059407 A059408 A059409

Keyword

nonn

Author

Robert G. Wilson v, Jan 29 2001

Status

approved