cp's OEIS Frontend

A348751 Numbers k for which A348750(k) < k.

%I A348751 #5 Nov 03 2021 18:30:27
%S A348751 2,3,5,6,7,8,10,11,13,14,15,17,18,19,21,22,23,24,26,27,29,30,31,33,34,
%T A348751 35,37,38,39,40,41,42,43,44,45,46,47,50,51,52,53,54,55,56,57,58,59,60,
%U A348751 61,62,63,65,66,67,68,69,70,71,73,74,75,76,77,78,79,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97
%N A348751 Numbers k for which A348750(k) < k.
%o A348751 (PARI)
%o A348751 A003961(n) = my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); \\ From A003961
%o A348751 A064989(n) = {my(f); f = factor(n); if((n>1 && f[1,1]==2), f[1,2] = 0); for (i=1, #f~, f[i,1] = precprime(f[i,1]-1)); factorback(f)};
%o A348751 A348750(n) = A064989(A064989(sigma(A003961(A003961(n)))));
%o A348751 isA348752(n) = (A348750(n)>n);
%Y A348751 Cf. A003961, A064989, A348750, A348751.
%Y A348751 Cf. A348753 (corresponding 5-rough numbers, terms of A007310).
%K A348751 nonn
%O A348751 1,1
%A A348751 _Antti Karttunen_, Nov 02 2021