OFFSET
1,1
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..1000
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
KEYWORD
nonn,easy,base
AUTHOR
Michel Lagneau, Oct 05 2012
STATUS
approved