A378985 Number of iterations of x -> A003961(x) needed before the result is deficient, when starting from x = 2*n.

0, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 0, 0, 2, 0, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 2, 0, 0, 1, 0, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 1, 0, 0, 1, 0, 0, 2

Offset

1,60

Comments

This grows slowly. See comments in A336835.

Links

Antti Karttunen, Table of n, a(n) for n = 1..100000

Index entries for sequences related to prime indices in the factorization of n.

Index entries for sequences related to sigma(n).

Formula

a(n) = A336835(2*n).

Prog

(PARI)
A003961(n) = my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); \\ From A003961
A336835(n) = { my(i=0); while(sigma(n) >= (n+n), i++; n = A003961(n)); (i); };
A378985(n) = A336835(2*n);

Crossrefs

Even bisection of A336835.

Cf. A000203, A003961.

Cf. arrays A341605, A378979.

Sequence in context: A341354 A203945 A212663 * A341774 A015692 A016232

Adjacent sequences: A378982 A378983 A378984 * A378986 A378987 A378988

Keyword

nonn

Author

Antti Karttunen, Dec 13 2024

Status

approved