A078494 - OEIS

A078494

Primes occurring only once in their decade.

97, 113, 127, 149, 181, 211, 241, 293, 307, 367, 397, 419, 421, 457, 479, 487, 557, 587, 631, 661, 683, 691, 719, 727, 743, 773, 787, 797, 809, 811, 839, 863, 877, 907, 929, 937, 953, 967, 983, 1009, 1021, 1049, 1051, 1087, 1117, 1163, 1171, 1193, 1201, 1249

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OFFSET

1,1

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..10000

FORMULA

a(n) ~ n log n. In particular, most primes are in this sequence. - Charles R Greathouse IV, Sep 07 2012

PROG

(PARI) decade1pr(n1, n2) = { forstep(x=n1, n2, 10, if(isprime(x+1) && !isprime(x+3) && !isprime(x+7) && !isprime(x+9), print1(x+1" "); ); if(isprime(x+3) && !isprime(x+1) && !isprime(x+7) && !isprime(x+9), print1(x+3" "); ); if(isprime(x+7) && !isprime(x+1) && !isprime(x+3) && !isprime(x+9), print1(x+7" "); ); if(isprime(x+9) && !isprime(x+1) && !isprime(x+3) && !isprime(x+7), print1(x+9" "); ); ); }

(Magma) &cat [PrimesInInterval(10*n+1, 10*n+9): n in [0..150] | IsOne(#PrimesInInterval(10*n+1, 10*n+9))]; // Bruno Berselli, Sep 05 2012

CROSSREFS

Cf. A078500.

Sequence in context: A033202 A160032 A136477 * A139980 A140830 A038133

Adjacent sequences: A078491 A078492 A078493 * A078495 A078496 A078497

KEYWORD

nonn,easy,base

AUTHOR

Cino Hilliard, Jan 04 2003

STATUS

approved