A105407 Indices n of primes p(n), p(n+4) such that p(n)-1 and p(n+4)-1 have the same largest prime factor.

3, 4, 8, 10, 21, 25, 54, 67, 122, 304, 436, 640, 647, 1106, 1917, 2292, 3622, 3783, 10285, 10600, 14785, 20211, 21804, 137507, 383436, 413254, 662294, 766759, 841376, 880622, 1406141, 1882958, 2051870, 2896609, 3033094, 3201710, 4937565, 6544495, 19611983, 33204098, 40184934, 473909315, 475815668, 662860224, 889407349

Offset

1,1

Links

Table of n, a(n) for n=1..45.

Prog

(PARI) \prime indices such that gd of prime(x)+ k and prime(x+m) + k are equal divpm1(n, m, k) = { local(x, l1, l2, v1, v2); for(x=2, n, v1 = ifactor(prime(x)+ k); v2 = ifactor(prime(x+m)+k); l1 = length(v1); l2 = length(v2); if(v1[l1] == v2[l2], print1(x", ") ) ) } ifactor(n) = \Vector of the prime factors of n { local(f, j, k, flist); flist=[]; f=Vec(factor(n)); for(j=1, length(f[1]), for(k = 1, f[2][j], flist = concat(flist, f[1][j]) ); ); return(flist) }

Crossrefs

Sequence in context: A233771 A072606 A098764 * A222395 A222269 A310011

Adjacent sequences: A105404 A105405 A105406 * A105408 A105409 A105410

Keyword

nonn

Author

Cino Hilliard, May 01 2005

Extensions

8 more terms from R. J. Mathar, Feb 14 2008

a(32)-a(45) from Donovan Johnson, Apr 03 2008

Status

approved