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A306532 Composite numbers k such that the sum of their aliquot parts divides k+1. 1
21, 115, 329, 731, 2133, 2171, 6821, 7379, 8357, 13987, 19521, 24331, 24881, 29491, 46001, 50579, 56789, 79421, 103729, 117409, 125159, 137881, 174109, 176661, 226859, 235721, 257291, 357769, 492071, 499091, 560537, 584021, 704791, 776341, 822857, 850607, 908981 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..37.

EXAMPLE

Aliquot parts of 21 are 1, 3, 7 and 22/(1+3+7) = 22/11 = 2.

MAPLE

with(numtheory): P:=proc(n) if not isprime(n) and frac((n+1)/(sigma(n)-n))=0 then n; fi; end: seq(P(i), i=2..100000);

PROG

(PARI) isok(n) = (n!=1) && !isprime(n) && !frac((n+1)/(sigma(n)-n)); \\ Michel Marcus, Feb 28 2019

CROSSREFS

Cf. A203966, A306531.

Sequence in context: A129135 A158091 A121628 * A219154 A054257 A297316

Adjacent sequences:  A306529 A306530 A306531 * A306533 A306534 A306535

KEYWORD

nonn,easy

AUTHOR

Paolo P. Lava, Feb 22 2019

STATUS

approved

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Last modified August 10 03:47 EDT 2020. Contains 336368 sequences. (Running on oeis4.)