A341618 - OEIS

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A341618

a(n) = 0 if n is not a primitive nondeficient number, otherwise a(n) is the number of primitive nondeficient divisors of the last number in the iteration x -> A003961(x) (starting from x=n) for which that count (A337690) is nonzero.

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

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OFFSET

1,60

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..65537

Index entries for sequences computed from indices in prime factorization

Index entries for sequences related to sigma(n)

PROG

(PARI)

A341619(n) = if(sigma(n) < (2*n), 0, fordiv(n, d, if((d<n)&&(sigma(d) >= 2*d), return(0))); (1)); \\ After code in A071395

A337690(n) = sumdiv(n, d, A341619(d));

A003961(n) = { my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };

A341618(n) = { my(t, u=0); while((t=A337690(n))>0, u=t; n = A003961(n)); (u); };

CROSSREFS

Differs from A337690 for the first time at n=120, where a(120)=1, while A337690(120)=2.

Cf. A006039, A341508, A341619, A341624.

Sequence in context: A261488 A341353 A010105 * A337690 A083916 A083893

Adjacent sequences: A341615 A341616 A341617 * A341619 A341620 A341621

KEYWORD

nonn

AUTHOR

Antti Karttunen, Feb 21 2021

STATUS

approved