cp's OEIS Frontend

A363175 Primitive abundant numbers (A071395) that are powerful numbers (A001694).

%I A363175 #13 May 19 2023 08:02:19
%S A363175 342225,570375,3172468,4636684,63126063,99198099,117234117,171991125,
%T A363175 280495504,319600125,327921075,404529741,581549787,635689593,
%U A363175 762155163,1029447225,1148667664,1356949503,1435045924,1501500375,1558495125,1596961444,1757705625,1778362047
%N A363175 Primitive abundant numbers (A071395) that are powerful numbers (A001694).
%C A363175 The least cubefull (A036966) term is a(154) = A363177(1) = 26376098024367 = 3^6 * 7^4 * 13^3 * 19^3.
%H A363175 Amiram Eldar, <a href="/A363175/b363175.txt">Table of n, a(n) for n = 1..2145</a> (terms below 10^18)
%H A363175 Wikipedia, <a href="https://en.wikipedia.org/wiki/Powerful_number">Powerful number</a>.
%H A363175 Wikipedia, <a href="https://en.wikipedia.org/wiki/Primitive_abundant_number">Primitive abundant number</a>.
%t A363175 f1[p_, e_] := (p^(e + 1) - 1)/(p^(e + 1) - p^e); f2[p_, e_] := (p^(e + 1) - p)/(p^(e + 1) - 1);
%t A363175 primAbQ[n_] := (r = Times @@ f1 @@@ (f = FactorInteger[n])) > 2 && r * Max @@ f2 @@@ f < 2;
%t A363175 seq[max_] := Module[{pow = Union[Flatten[Table[i^2*j^3, {j, 1, max^(1/3)}, {i, 1, Sqrt[max/j^3]}]]]}, Select[Rest[pow], primAbQ]]; seq[10^10]
%o A363175 (PARI) isPrimAb(n) = {my(f = factor(n), r, p, e); r = sigma(f, -1); r > 2 && vecmax(vector(#f~, i, p = f[i, 1]; e = f[i, 2]; (p^(e + 1) - p)/(p^(e + 1) - 1))) * r < 2; }
%o A363175 lista(lim) = {my(pow = List(), t); for(j=1, sqrtnint(lim\1, 3), for(i=1, sqrtint(lim\j^3), listput(pow, i^2*j^3))); select(x->isPrimAb(x), Set(pow)); }
%Y A363175 Intersection of A001694 and A071395.
%Y A363175 Subsequence of A363169 and A363176.
%Y A363175 Subsequences: A306796, A306797, A363177.
%Y A363175 Cf. A036966.
%K A363175 nonn
%O A363175 1,1
%A A363175 _Amiram Eldar_, May 19 2023