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A224613 a(n) = sigma(6*n). 12
12, 28, 39, 60, 72, 91, 96, 124, 120, 168, 144, 195, 168, 224, 234, 252, 216, 280, 240, 360, 312, 336, 288, 403, 372, 392, 363, 480, 360, 546, 384, 508, 468, 504, 576, 600, 456, 560, 546, 744, 504, 728, 528, 720, 720, 672, 576, 819, 684, 868, 702, 840, 648 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Conjectures: sigma(6n) > sigma(6n - 1) and sigma(6n) > sigma(6n + 1).

Conjectures are false. Try prime 73961483429 for n. One finds sigma(6*73961483429) < sigma(6*73961483429+1). The number n = 105851369791 provides a counterexample for the other case. - T. D. Noe, Apr 22 2013

LINKS

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

FORMULA

a(n) = A000203(6n).

MATHEMATICA

DivisorSigma[1, 6*Range[60]] (* Harvey P. Dale, Apr 16 2016 *)

PROG

(PARI) a(n)=sigma(6*n) \\ Charles R Greathouse IV, Apr 22 2013

CROSSREFS

Sigma(k*n): A000203 (k=1), A062731 (k=2), A144613 (k=3), A193553 (k=4), this sequence (k=6), A283078 (k=7).

Cf. A000203 (sigma(n)), A053224 (n: sigma(n) < sigma(n+1)).

Cf. A067825 (even n: sigma(n)< sigma(n+1)).

Sequence in context: A255136 A087252 A141274 * A134618 A108405 A184838

Adjacent sequences:  A224610 A224611 A224612 * A224614 A224615 A224616

KEYWORD

nonn

AUTHOR

Zak Seidov, Apr 22 2013

EXTENSIONS

Corrected by Harvey P. Dale, Apr 16 2016

STATUS

approved

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Last modified December 8 09:32 EST 2019. Contains 329862 sequences. (Running on oeis4.)