A388020 Primitive terms of A023197 that are of the form 4u+2.

1890, 3150, 4410, 6930, 8190, 10710, 11550, 11970, 12870, 13650, 14490, 14850, 16170, 16830, 17850, 18270, 19110, 19530, 23310, 25410, 25830, 27090, 29610, 30030, 33390, 37170, 38430, 39270, 42210, 43890, 44730, 45990, 46410, 49770, 51870, 52290, 53130, 56070, 56430, 59670, 61110, 62790, 63630, 64890, 66690, 66990

Offset

1,1

Comments

The first term that is not a multiple of 3 is 10782822050 = 2*A115414(1).

Links

Antti Karttunen, Table of n, a(n) for n = 1..10000

Index entries for sequences related to sigma(n).

Formula

a(n) = 2*A006038(n). [Conjectured, not true if odd perfect numbers exist]

Prog

(PARI) is_A388020(n) = if(2!=(n%4) || (sigma(n)/n)<3, 0, fordiv(n, d, if(d<n && (sigma(d)/d)>=3, return(0))); (1));

Crossrefs

Intersection of A016825 and A388019.

Cf. A000203, A006038, A115414.

Cf. also A349745, A387163.

Sequence in context: A168226 A151721 A187743 * A251829 A251822 A251821

Adjacent sequences: A388017 A388018 A388019 * A388021 A388022 A388023

Keyword

nonn

Author

Antti Karttunen, Sep 15 2025

Status

approved