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A217390 Numbers n such that sum of squares of digits of n equals the sum of prime divisors of n. 3
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

n such that A003132(n) = A008472(n).

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

Cf. A003132, A008472.

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

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Last modified October 28 13:26 EDT 2021. Contains 348329 sequences. (Running on oeis4.)