A177714 a(n) = (A123571(n) - 2n - 1)/(2n).

5, 6, 12, 4, 3, 25, 29, 15, 29, 22, 45, 27, 89, 6, 21, 65, 39, 27, 116, 378, 67, 176, 162, 43, 101, 158, 14, 172, 26, 22, 40, 491, 54, 340, 141, 145, 224, 284, 1078, 65, 165, 22, 260, 266, 32, 253, 234, 715, 1025, 5, 163, 197, 380, 118, 221, 212, 353, 17, 585, 36, 245

Offset

1,1

Comments

For a(n) = m the prime p = A123571(n) is the least prime dividing m^(m+1)+1, where m = (p-2n-1)/(2n).

Links

Table of n, a(n) for n=1..61.

Formula

a(n) = (A123571(n) - 2n - 1)/(2n).

Prog

(PARI) A123571(n)={ local(m) ; forprime(p=1, 500000, if( (p-2*n-1) % (2*n) ==0, m=(p-2*n-1)/(2*n) ; if( (m^(m+1)+1) % p == 0, return(p) ; ) ; ) ; ) ; return(-1) ; }
A177714(n)={ return((A123571(n)-2*n-1)/(2*n)) ; }
{ for(n=1, 100, print1(A177714(n)", ") ; ) ; } \\ R. J. Mathar, May 28 2010

Crossrefs

Cf. A123571 (smallest prime p such that p divides m^(m+1)+1, where m = (p-2n-1)/(2n)).

Sequence in context: A362020 A328544 A041939 * A273158 A099641 A207189

Adjacent sequences: A177711 A177712 A177713 * A177715 A177716 A177717

Keyword

nonn

Author

Alexander Adamchuk, May 11 2010

Extensions

More terms from R. J. Mathar, May 28 2010

Status

approved