OFFSET
1,3
COMMENTS
For each j, the sequence A103782 constructs a prime of the form P(j)#*2^k - 1. If this is also a lower twin prime, then j is a term of this sequence.
EXAMPLE
P(0)# = 1, P(0)#*2^2 - 1 = 3, P(0)#*2^2 + 1 = 5 twin prime of 5 so a(1)=0;
P(1)# = 1*2, P(1)#*2^1 - 1 = 3, P(1)#*2^1 + 1 = 5 twin prime of 5 so a(2)=1;
P(2)# = 1*2*3, P(2)#*2^1 - 1 = 11, P(2)#*2^1 + 1 = 13 twin prime of 11 so a(3)=2.
MAPLE
isA001359 := proc(n) isprime(n) and isprime(n+2) ; end proc:
A002110 := proc(n) mul(ithprime(i), i=1..n) ; end proc:
A103782 := proc(n) local m ; for m from 0 do if isprime(A002110(n)*2^m-1) then return m; end if; end do: end proc:
for n from 0 do if isA177064(n) then print(n) ; end if; end do: # R. J. Mathar, Dec 12 2010
PROG
(PFGW & SCRIPT)
DIM nn, -1
DIM kk
DIMS tt
LABEL loopn
SET nn, nn+1
SET kk, -1
LABEL loopk
SET kk, kk+1
SETS tt, %d, %d\,; p(nn); kk
PRP p(nn)#*2^kk-1, tt
IF !(ISPRP || ISPRIME) THEN goto loopk
PRP p(nn)#*2^kk+1, tt
GOTO loopn
CROSSREFS
KEYWORD
nonn
AUTHOR
Pierre CAMI, Dec 09 2010
STATUS
approved