A307881 - OEIS

A307881

2*a(n) is the least number where k sets a new record such that 2*a(n)-k and 2*a(n)+k are prime and at least one of 2*a(n)-j and 2*a(n)+j is composite for all 0<j<k.

2, 4, 11, 23, 64, 68, 73, 119, 143, 172, 263, 452, 557, 868, 1238, 1579, 2864, 3533, 3637, 4252, 5171, 9263, 11282, 12388, 20036, 59119, 69332, 90131, 113783, 139283, 178612, 185714, 413788, 468059, 579932, 960707, 1879582, 2727031, 3266951, 3319868, 3591593

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OFFSET

1,1

COMMENTS

The corresponding records of k are given in A307882.

LINKS

Hugo Pfoertner, Table of n, a(n) for n = 1..53

PROG

(PARI) kmax=0; for(n=2, 10^7, forstep(k=1, n, 2, if(isprime(2*n-k)&&isprime(2*n+k), if(k>kmax, print1(n, ", "); kmax=k); break(1))))

CROSSREFS

Cf. A065978, A293858, A307882, A325142.

Sequence in context: A358082 A061152 A365045 * A006452 A104430 A298255

Adjacent sequences: A307878 A307879 A307880 * A307882 A307883 A307884

KEYWORD

nonn

AUTHOR

Hugo Pfoertner, May 03 2019

STATUS

approved