A073722 Least k such that sigma(k) mod primepi(k) = n or zero if no such number exists.

2, 4, 10, 8, 17, 42, 23, 111, 32, 59, 31, 67, 49, 110, 63, 60, 82, 84, 89, 75, 191, 98, 141, 97, 101, 256, 171, 169, 148, 144, 140, 159, 143, 222, 220, 172, 206, 2124, 183, 315, 263, 567, 201, 358, 204, 470, 243, 391, 264, 563, 295, 382, 290, 285, 313, 324, 307

Offset

0,1

Links

Sean A. Irvine, Table of n, a(n) for n = 0..10000

Formula

a(n) = min{x: A000203(x) mod A000720(x) = n}.

Example

n=8: a(8)=32 since sigma(32)=63, primepi(32)=11, and 63 mod 11 = 8.

Mathematica

t=Table[0, {100}]; Do[s=Mod[DivisorSigma[1, n], PrimePi[n]]; If[s<101&&t[[s]]==0, t[[s]]=n], {n, 2, 10000}]; t

Crossrefs

Cf. A000203, A000720, A072548, A073721-A073724.

Sequence in context: A227289 A200742 A178729 * A124108 A173824 A356603

Adjacent sequences: A073719 A073720 A073721 * A073723 A073724 A073725

Keyword

nonn

Author

Labos Elemer, Aug 05 2002

Extensions

a(0)=2 inserted by Sean A. Irvine, Dec 16 2024

Status

approved