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 A272191 Either 8th power of a prime, or product of a square and a cube of two different primes. 1
 72, 108, 200, 256, 392, 500, 675, 968, 1125, 1323, 1352, 1372, 2312, 2888, 3087, 3267, 4232, 4563, 5324, 6125, 6561, 6728, 7688, 7803, 8575, 8788, 9747, 10952, 11979, 13448, 14283, 14792, 15125, 17672, 19652, 19773, 21125, 22472, 22707, 25947, 27436, 27848, 29768 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Numbers such that the sum of the number of divisors of their aliquot parts is four times the number of their divisors. LINKS EXAMPLE 72 = 2^3 * 3^2;  256 = 2^8. MAPLE with(numtheory): P:=proc(q) local a, k, n;  for n from 2 to q do a:=sort([op(divisors(n))]); if 4*tau(n)= add(tau(a[k]), k=1..nops(a)-1) then print(n); fi; od; end: P(10^7); PROG (PARI) isok(n) = 4*numdiv(n) == sumdiv(n, d, (n!=d)*numdiv(d)); \\ Michel Marcus, Apr 22 2016 CROSSREFS Cf. A030516, A143610, A179645, A272190. Sequence in context: A216426 A308053 A307758 * A072412 A052486 A114128 Adjacent sequences:  A272188 A272189 A272190 * A272192 A272193 A272194 KEYWORD nonn,easy AUTHOR Paolo P. Lava, Apr 22 2016 STATUS approved

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Last modified May 15 04:03 EDT 2021. Contains 343909 sequences. (Running on oeis4.)