A114739 - OEIS

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A114739

a(1) = 1. Smallest prime == 1 (mod n) if n is composite else least composite number ==1 (mod n).

1, 9, 4, 5, 6, 7, 8, 17, 19, 11, 12, 13, 14, 29, 31, 17, 18, 19, 20, 41, 43, 23, 24, 73, 101, 53, 109, 29, 30, 31, 32, 97, 67, 103, 71, 37, 38, 191, 79, 41, 42, 43, 44, 89, 181, 47, 48, 97, 197, 101, 103, 53, 54, 109, 331, 113, 229, 59, 60, 61

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..60.

PROG

(PARI) a(n) = {if (n == 1, return (1)); k = 1; if (! isprime(n), while (! isprime(k*n+1), k++), while (isprime(k*n+1), k++)); k*n+1; } \\ Michel Marcus, Sep 17 2013

CROSSREFS

Sequence in context: A019880 A021518 A030070 * A240964 A154900 A246546

Adjacent sequences: A114736 A114737 A114738 * A114740 A114741 A114742

KEYWORD

nonn,less

AUTHOR

Amarnath Murthy, Nov 15 2005

EXTENSIONS

a(3) corrected and more terms added by Michel Marcus, Sep 17 2013

STATUS

approved