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A193437 E.g.f.: exp( Sum_{n>=0} x^(3*n+1)/(3*n+1) ). 1
1, 1, 1, 1, 7, 31, 91, 931, 7441, 38017, 507241, 5864761, 43501591, 713059711, 10776989587, 105784464331, 2052437475361, 38263122487681, 469863736958161, 10518597616325617, 232980391759702951, 3446848352553524191, 87385257330831947851 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

Conjecture: a(n) is divisible by 7^floor(n/7) for n>=0.

Conjecture: a(n) is divisible by p^floor(n/p) for prime p == 1 (mod 3).

LINKS

Table of n, a(n) for n=0..22.

EXAMPLE

E.g.f.: A(x) = 1 + x + x^2/2! + x^3/3! + 7*x^4/4! + 31*x^5/5! + 91*x^6/6! + 931*x^7/7! +...

where

log(A(x)) = x + x^4/4 + x^7/7 + x^10/10 + x^13/13 + x^16/16 + x^19/19 +...

PROG

(PARI) {a(n)=n!*polcoeff( exp(sum(m=0, n, x^(3*m+1)/(3*m+1))+x*O(x^n)) , n)}

CROSSREFS

Cf. A193438.

Sequence in context: A118935 A226838 A205801 * A199921 A192596 A055899

Adjacent sequences:  A193434 A193435 A193436 * A193438 A193439 A193440

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Jul 25 2011

STATUS

approved

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Last modified January 17 23:37 EST 2020. Contains 330995 sequences. (Running on oeis4.)