A306532 Composite numbers k such that the sum of their aliquot parts divides k+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

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 A341570

Adjacent sequences: A306529 A306530 A306531 * A306533 A306534 A306535

Keyword

nonn,easy

Author

Paolo P. Lava, Feb 22 2019

Status

approved