A213420 Smallest number k such that the sum of prime factors of k (counted with multiplicity) is n times a square > 1.
4, 15, 35, 39, 51, 95, 115, 87, 155, 111, 123, 215, 235, 159, 371, 183, 302, 335, 219, 511, 395, 415, 267, 623, 291, 303, 482, 327, 339, 791, 554, 1415, 635, 655, 411, 695, 662, 447, 698, 471, 734, 815, 835, 519, 1211, 543, 842, 1991, 579, 591, 914, 2167, 2587
Offset: 1
Keywords
Examples
a(105) = 3764 because 3764 = 2^2 * 941 and the sum of prime factors (counted with multiplicity) is 4 + 941 = 945 = 105*9 where 9 is a square.
Links
- Amiram Eldar, Table of n, a(n) for n = 1..10000
Programs
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Maple
with(numtheory): sopfr:= proc(n) option remember; add(i[1]*i[2], i=ifactors(n)[2]) end: a:= proc(n) local k, p; for k from 2 while irem(sopfr(k), n, 'p')>0 or sqrt(p)<>floor(sqrt(p)) or p=1 do od; k end: seq (a(n), n=1..100);
Comments