A085649 - OEIS

A085649

Brilliant numbers k such that 2k+1 is also brilliant.

4, 10, 533, 671, 869, 1139, 2279, 14873, 17819, 20651, 22523, 23129, 23381, 25199, 28013, 28943, 31439, 31571, 33899, 35369, 35621, 37241, 37403, 39059, 39449, 41291, 42401, 42431, 42881, 43259, 45173, 45803, 49583, 49649, 49949, 50621

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..36.

EXAMPLE

1139 is a member because 1139 = 17*67 and 1139*2+1 = 2279 = 43*53.

PROG

(PARI) isA078972(k)={my(f=factor(k)); bigomega(f)==2 && (f[1, 2]==2 || logint(f[1, 1], 10)==logint(f[2, 1], 10))}

isok(k)={isA078972(k) && isA078972(2*k+1)} \\ Andrew Howroyd, Sep 18 2024

CROSSREFS

Subsequence of A111153.

Cf. A078972.

Sequence in context: A220197 A299880 A358928 * A152396 A326720 A307491

Adjacent sequences: A085646 A085647 A085648 * A085650 A085651 A085652

KEYWORD

base,nonn

AUTHOR

Jason Earls, Amarnath Murthy, Jul 11 2003

EXTENSIONS

Offset changed by Andrew Howroyd, Sep 18 2024

STATUS

approved