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Numbers k, not powers of primes, such that A336456(k) = Product_{p^e|k} A336456(p^e). Here each p^e is the maximal power of prime p that divides k, and A336456(k) = A335915(sigma(sigma(k))).
6

%I #7 Jul 27 2020 21:09:56

%S 6,12,14,15,18,20,24,26,28,36,38,39,44,45,48,50,51,54,56,60,62,63,68,

%T 72,74,75,76,78,80,86,87,92,95,96,99,100,104,108,111,112,116,117,122,

%U 123,124,126,134,143,144,146,147,148,150,153,158,159,162,171,172,175,176,180,183,188,192,194,196,200,204,206,207

%N Numbers k, not powers of primes, such that A336456(k) = Product_{p^e|k} A336456(p^e). Here each p^e is the maximal power of prime p that divides k, and A336456(k) = A335915(sigma(sigma(k))).

%H Antti Karttunen, <a href="/A336559/b336559.txt">Table of n, a(n) for n = 1..25000</a>

%o (PARI) isA336559(n) = ((n>1) && !isprimepower(n) && A336556(n)); \\ Needs also code from A336556.

%Y Terms of A336557 without those of A000961.

%Y Cf. A335915, A336456, A336556, A336558, A336560.

%Y Cf. A336549 (a subsequence).

%K nonn

%O 1,1

%A _Antti Karttunen_, Jul 25 2020