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A333694 G.f.: Sum_{k>=1} k * x^k / (1 - x^(k^2)). 1
1, 3, 4, 5, 6, 9, 8, 9, 10, 13, 12, 16, 14, 17, 16, 17, 18, 21, 20, 25, 25, 25, 24, 25, 26, 29, 28, 29, 30, 41, 32, 33, 34, 37, 36, 41, 38, 41, 43, 41, 42, 51, 44, 45, 46, 49, 48, 52, 50, 53, 52, 57, 54, 57, 61, 64, 61, 61, 60, 61, 62, 65, 64, 65, 66, 72, 68, 73, 70, 73 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Sum of divisors d of n such that n/d == 1 (mod d).

LINKS

Table of n, a(n) for n=1..70.

MAPLE

a:= n-> add(`if`(irem(n/d-1, d)=0, d, 0), d=numtheory[divisors](n)):

seq(a(n), n=1..80);  # Alois P. Heinz, Apr 04 2020

MATHEMATICA

nmax = 70; CoefficientList[Series[Sum[k x^k/(1 - x^(k^2)), {k, 1, nmax}], {x, 0, nmax}], x] // Rest

Table[DivisorSum[n, # &, Mod[n/# - 1, #] == 0 &], {n, 1, 70}]

PROG

(PARI) A333694(n) = sumdiv(n, d, d*(0==(((n/d)-1)%d))); \\ Antti Karttunen, Apr 04 2020, after the second Mathematica program.

CROSSREFS

Cf. A000203, A069290, A163671.

Sequence in context: A037348 A277898 A212640 * A338321 A220844 A047250

Adjacent sequences:  A333691 A333692 A333693 * A333695 A333696 A333697

KEYWORD

nonn

AUTHOR

Ilya Gutkovskiy, Apr 04 2020

STATUS

approved

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Last modified September 17 16:17 EDT 2021. Contains 347487 sequences. (Running on oeis4.)