OFFSET
1,1
FORMULA
a(n)=min(k>0, k has the same sum of squares of divisors as A131905(n))
EXAMPLE
a(5)=66 because A131905(5)=77 and the sum of the squares of the divisors of 77 is 1+49+121+5929=6100 and the sum of the squares of the divisors of 66 is 1+4+9+36+121+484+1089+4356=6100 and there is no smaller positive integer with this squaresum of its divisors
MATHEMATICA
Clear[tmp]; Last@Transpose[ Function[n, (If[Head[ #1] === tmp, #1 = n; Unevaluated[Sequence[]], {n, #1}] & )[tmp[DivisorSigma[2, n]]]] /@ Range[500]]
PROG
(PARI) lista(nn) = {for (n=1, nn, my(sn = sigma(n, 2)); for (k=1, n-1, if (sigma(k, 2) == sn, print1(k, ", "); break); ); ); } \\ Michel Marcus, Apr 03 2015
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Peter Pein (petsie(AT)dordos.net), Jul 26 2007
EXTENSIONS
More terms from Michel Marcus, Apr 03 2015
STATUS
approved