A391844 a(n) = 1 if the least prime not dividing the arithmetic derivative of n is equal to the least prime dividing n, otherwise 0. a(1) = 1 by convention.

1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 1, 1, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1

Offset

1

Links

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

Index entries for characteristic functions.

Prog

(PARI)
A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));
A020639(n) = if(1==n, n, vecmin(factor(n)[, 1]));
A053669(n) = forprime(p=2, , if(n%p, return(p))); \\ From A053669
A391844(n) = if(n<2, n, (A053669(A003415(n))==A020639(n)));

Crossrefs

Characteristic function of A391845.

Cf. A003415, A020639, A053669.

Cf. also A370124.

Sequence in context: A379117 A185059 A179776 * A360130 A353570 A089802

Adjacent sequences: A391841 A391842 A391843 * A391845 A391846 A391847

Keyword

nonn

Author

Antti Karttunen, Jan 16 2026

Status

approved