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A130971 Smallest prime p, such that either |A000040(n)-p| or A000040(n)+p is of the form 2^k. 4
2, 2, 3, 3, 3, 3, 13, 3, 7, 3, 23, 5, 23, 11, 17, 11, 5, 3, 3, 7, 41, 47, 19, 73, 31, 37, 71, 43, 19, 97, 131, 3, 73, 11, 107, 23, 29, 131, 89, 83, 163, 53, 127, 191, 59, 71, 83, 191, 29, 101, 23, 17, 113, 5, 193, 7, 13, 239, 149, 277, 229, 37, 179, 307, 199, 61, 181, 353, 283 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Ray Chandler, Table of n, a(n) for n=1..10000

PROG

(Scheme:) (define (A130971 n) (let ((p1 (A000040 n))) (let loop ((i 1) (p2 2)) (cond ((pow2? (abs (- p1 p2))) p2) ((pow2? (+ p1 p2)) p2) (else (loop (+ i 1) (A000040 (+ i 1))))))))

(define (pow2? n) (and (> n 0) (zero? (A004198bi n (- n 1)))))

CROSSREFS

Cf. A130971, A130972, A103150.

Sequence in context: A239496 A299962 A128586 * A051776 A270920 A262956

Adjacent sequences:  A130968 A130969 A130970 * A130972 A130973 A130974

KEYWORD

nonn

AUTHOR

Antti Karttunen, Jun 19 2007

EXTENSIONS

Extended by Ray Chandler, Aug 06 2010

STATUS

approved

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Last modified January 23 01:30 EST 2020. Contains 331166 sequences. (Running on oeis4.)