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A248189 Least positive integer m such that m*n divides sigma(m^2+n^2), where sigma(k) is the sum of all positive divisors of k. 2
1, 1, 1, 7, 2, 38, 4, 81, 1, 102, 868, 1, 9, 3, 702, 26505, 1554, 14, 3, 243, 1, 650, 108, 1833, 34542, 18, 68, 186, 7252, 39, 58, 736839, 1, 3108, 72, 778, 210, 6, 3, 4830, 267, 2, 567, 5859, 6640, 6363, 3178412, 155771, 4964, 9 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,4
COMMENTS
Conjecture: a(n) exists for any n > 0.
See also the comments in A248058.
LINKS
EXAMPLE
a(6) = 38 since 6*38 = 228 divides sigma(6^2+38^2) = sigma(1480) = 3420 = 15*228.
MATHEMATICA
Do[m=1; Label[aa]; If[Mod[DivisorSigma[1, m^2+n^2], m*n]==0, Print[n, " ", m]; Goto[bb]]; m=m+1; Goto[aa]; Label[bb]; Continue, {n, 1, 50}]
PROG
(PARI)
a(n)=m=1; while(sigma(n^2+m^2)%(m*n), m++); m
n=1; while(n<50, print1(a(n), ", "); n++) \\ Derek Orr, Oct 03 2014
CROSSREFS
Sequence in context: A282799 A222555 A246799 * A096040 A038268 A100983
KEYWORD
nonn
AUTHOR
Zhi-Wei Sun, Oct 03 2014
STATUS
approved

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Last modified April 14 10:04 EDT 2024. Contains 371657 sequences. (Running on oeis4.)