A217390 Numbers k such that sum of squares of digits of k equals the sum of prime divisors of k.

12, 581, 1014, 1036, 1180, 1272, 1746, 2553, 3420, 3741, 4140, 4544, 5104, 5238, 5313, 5966, 7134, 7272, 8174, 8346, 8549, 9153, 9525, 9536, 10476, 11070, 11800, 12350, 12882, 13481, 13702, 14045, 15341, 15974, 16415, 16999, 17051, 17220, 17444, 18361, 18798

Offset

1,1

Comments

Numbers k such that A003132(k) = A008472(k).

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Andrew Howroyd)

Example

581 = 7*83 is in the sequence because 5^2 + 8^2 + 1^2 = 7 + 83 = 90.

Maple

with(numtheory):A:= proc(n) add(u^2, u=convert(n, base, 10)) ; end proc: for i from 2 to 20000 do:x:=factorset(i):n1:=nops(x): s:=sum('x[i] ', 'i'=1..n1):if s=A(i) then printf(`%d, `, i):else fi:od:

Mathematica

Rest[Select[Range[20000], Total[Transpose[FactorInteger[#]][[1]]]==Total[IntegerDigits[#]^2]&]]

Prog

(PARI) ok(n)={vecsum(factor(n)[, 1]) == vecsum(apply(d->d^2, digits(n)))} \\ Andrew Howroyd, Feb 25 2018

Crossrefs

Cf. A003132, A008472.

Cf. A070275, A217531, A217532, A217533.

Sequence in context: A307948 A042111 A159644 * A219103 A219982 A329024

Adjacent sequences: A217387 A217388 A217389 * A217391 A217392 A217393

Keyword

nonn,easy,base

Author

Michel Lagneau, Oct 05 2012

Status

approved