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A203556 a(n) = sigma(n^5). 3
1, 63, 364, 2047, 3906, 22932, 19608, 65535, 88573, 246078, 177156, 745108, 402234, 1235304, 1421784, 2097151, 1508598, 5580099, 2613660, 7995582, 7137312, 11160828, 6728904, 23854740, 12207031, 25340742, 21523360, 40137576, 21243690, 89572392, 29583456, 67108863 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n) modulo 6 begins: [1,3,4,1,0,0,0,3,1,0,0,4,0,0,0,1,0,3,0,0,0,0,0,0,1,0,...], in which positions of nonzero residues seem related to squares.

LINKS

Seiichi Manyama, Table of n, a(n) for n = 1..10000

FORMULA

Logarithmic derivative of A203557.

Multiplicative with a(p^e) = (p^(5*e+1)-1)/(p-1) for prime p. - Andrew Howroyd, Jul 23 2018

EXAMPLE

L.g.f.: L(x) = x + 63/2*x^2 + 364/3*x^3 + 2047/4*x^4 + 3906/5*x^5 +...

where the g.f. of A203557 begins:

exp(L(x)) = 1 + x + 32*x^2 + 153*x^3 + 1145*x^4 + 5677*x^5 + 37641*x^6 +...

PROG

(PARI) a(n) = sigma(n^5)

CROSSREFS

Cf. A203557 (exp), A000203 (sigma); variants: A065764, A175926, A202994.

Sequence in context: A160674 A034817 A160895 * A038993 A068022 A131993

Adjacent sequences:  A203553 A203554 A203555 * A203557 A203558 A203559

KEYWORD

nonn,mult

AUTHOR

Paul D. Hanna, Jan 03 2012

EXTENSIONS

Keyword:mult added by Andrew Howroyd, Jul 23 2018

STATUS

approved

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Last modified May 24 20:53 EDT 2019. Contains 323534 sequences. (Running on oeis4.)