A188673 a(n) = smallest semiprime such that prime(n) = a(n) - p, p prime.

4, 6, 10, 9, 14, 15, 22, 21, 25, 34, 33, 39, 46, 46, 49, 55, 62, 74, 69, 74, 86, 82, 85, 91, 134, 106, 106, 118, 111, 115, 129, 133, 142, 141, 166, 158, 159, 166, 169, 178, 202, 183, 194, 206, 202, 201, 213, 226, 274, 302, 235, 262, 254, 253, 259, 265, 274, 274, 314, 298, 302

Offset

1,1

Links

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

Example

a(1) =  4 because prime(1) =  4 - 2;
a(2) =  6 because prime(2) =  6 - 3;
a(3) = 10 because prime(3) = 10 - 5;
a(4) =  9 because prime(4) =  9 - 2;
a(5) = 14 because prime(5) = 14 - 3.

Maple

isA001358 := proc(n) return(numtheory[bigomega](n) = 2) ; end proc:
A188673 := proc(n) local p, j ; p := ithprime(n) ; for j from 1 do if isA001358(p+ithprime(j)) then return p+ithprime(j) ; end if; end do; end proc: # R. J. Mathar, Apr 16 2011

Crossrefs

Cf. A000040, A001358.

Sequence in context: A249982 A292767 A117622 * A365448 A193951 A129854

Adjacent sequences: A188670 A188671 A188672 * A188674 A188675 A188676

Keyword

nonn

Author

Michel Lagneau, Apr 14 2011

Status

approved