A350120 a(n) is the least integer k such that A350090(k) = 2*n-1 or -1 if no such k exists.

1, 5, 22, 33, 5951, 124, 90088, 187, 757, 1149, 237152823, 852, 30744479715, 207737, 15555, 876, 40828735337636, 1541, 2932093694892923, 8454, 3557030, 802103321, 1895798161468690610

Offset

1,2

Comments

Most terms of A350090 are odd. It is conjectured by Klaus Purath that all odd numbers appear in A350090.

a(n) is the least k such that tau(3*k*(k+1)+1) = 2*n. - Jinyuan Wang, Dec 19 2021

a(11) >= 10^8 if it exists. - Michel Marcus, Dec 20 2021

Links

Table of n, a(n) for n=1..23.

Prog

(PARI) a(n) = my(k=1, m=2*n); while (numdiv(3*k*(k+1)+1) != m, k++); k; \\ Michel Marcus, Dec 20 2021

Crossrefs

Cf. A000005 (tau), A002378, A003215, A350090.

Sequence in context: A283758 A288676 A085101 * A290510 A184724 A082005

Adjacent sequences: A350117 A350118 A350119 * A350121 A350122 A350123

Keyword

nonn,more

Author

Michel Marcus, Dec 15 2021

Extensions

a(11)-a(23) from Klaus Purath, Jan 04 2022

Status

approved