A033832 Sum of odd divisors of n < sqrt(n) = sum of even divisors of n < sqrt(n).

1, 40, 100, 208, 928, 1044, 3904, 10692, 17444, 29524, 36652, 45980, 87604, 91044, 136808, 158652, 161564, 171028, 187068, 218652, 230044, 260608, 287868, 406812, 438124, 450492, 583110, 665684, 719550, 731850, 736648, 865444, 1045504

Offset

1,2

Comments

All terms except first one appear to be even. - Michel Marcus, Jul 15 2013

Links

Amiram Eldar, Table of n, a(n) for n = 1..500

kaleidoscopic numbers [broken link]

Mathematica

aQ[n_] := DivisorSum[n, # * (-1)^# &, # < Sqrt[n] & ] == 0; Select[Range[10^4], aQ] (* Amiram Eldar, Sep 23 2019 *)

Prog

(PARI) isok(n) = {so = 0; se = 0; fordiv (n, d, if (d < sqrt(n), if (d % 2, so += d, se += d))); return (so == se); } \\ Michel Marcus, Jul 14 2013

Crossrefs

Cf. A070039, A113184.

Sequence in context: A092889 A235280 A235271 * A235017 A043219 A039396

Adjacent sequences: A033829 A033830 A033831 * A033833 A033834 A033835

Keyword

easy,nonn

Author

Naohiro Nomoto

Extensions

Prepended a(1)=1, Michel Marcus, Jul 15 2013

Status

approved