A090689 Repeated primes in first occurrence in the progression kx^2-1.

3, 7, 19, 43, 59, 67, 83, 89, 103, 107, 131, 139, 163, 179, 197, 199, 211, 223, 227, 251, 263, 283, 307, 311, 331, 347, 359, 367, 379, 383, 419, 443, 463, 467, 479, 487, 491, 499, 503, 521, 523, 547, 563, 571, 587, 619, 643, 647, 659, 683, 691, 739, 743, 751

Offset

1,1

Comments

These primes are of the form 4n+3 but some primes of the form 4n+3 such as 11,23,31,47, etc. are excluded. The program generates the duplicates. All but one were removed manually.

Links

Table of n, a(n) for n=1..54.

Example

467 occurs 3 times in the first occurrence for combinations of k and x in kx^2-1.

Prog

(PARI) mx2pmp(n, m) = { v=vector(n+1); c=0; for(a=1, n, for(x=1, n, y = a*x^2-1; if(isprime(y), c++; v[c]=y; break); ); ); v1=vecsort(v); for(j=1, n, if(v1[j]<>0 && v1[j]==v1[j+1], print1(v1[j]", "))) }

Crossrefs

Sequence in context: A282024 A356617 A086519 * A145476 A374841 A126938

Adjacent sequences: A090686 A090687 A090688 * A090690 A090691 A090692

Keyword

easy,nonn

Author

Cino Hilliard, Dec 18 2003

Status

approved