A365429 a(n) = 1 if the divisors of n increase by a factor of at most 2, otherwise 0.

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

Offset

1

Links

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

Index entries for characteristic functions

Formula

a(n) <= A322860(n). [Conjectured, see comment in A174973]

Prog

(PARI) A365429(n) = { my(d=divisors(n)); for(i=2, #d, if(d[i]>2*d[i-1], return(0))); (1); }; \\ From "is" function given in A174973

Crossrefs

Characteristic function of A174973.

Cf. A322860.

Sequence in context: A322585 A326956 A341629 * A322860 A378550 A353766

Adjacent sequences: A365426 A365427 A365428 * A365430 A365431 A365432

Keyword

nonn

Author

Antti Karttunen, Oct 22 2023

Status

approved