A101416 - OEIS

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A101416

Nearest k to j such that k*(2^j-1)-1 is prime where j=A000043(n) and 2^j-1 = Mersenne-prime(n) = A000668(n). If there are two k values equidistant from j, each of which produces a prime, the larger of the two gets added to the sequence.

2, 2, 2, 6, 20, 14, 32, 90, 72, 80, 230, 80, 560, 740, 1542, 1782, 450, 828, 2562, 3936, 12474, 9288, 10224, 16022, 11088, 31034, 53972, 92372

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..28.

EXAMPLE

n=7, j=A000043(7)=19, A000668(7)=524287, then k=6 or k=32 are the nearest values to j which produce primes so we take the larger of the two k values for a(7)=32.

CROSSREFS

Cf. A000043, A000668, A098555, A159585.

Sequence in context: A025248 A213170 A321741 * A371919 A098920 A270557

Adjacent sequences: A101413 A101414 A101415 * A101417 A101418 A101419

KEYWORD

hard,nonn

AUTHOR

Pierre CAMI, Jan 16 2005

EXTENSIONS

a(5)=20, a(20)=3936 corrected, other terms verified, a(27)-a(28) extended by Ray Chandler, Apr 16 2009

STATUS

approved