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 A177064 Primorial indices j such that P(j)#*2^k - 1 is a lower twin prime for the minimal k selected in A103782. 0
 0, 1, 2, 3, 4, 5, 9, 30, 96, 148, 171, 201, 246, 274, 294, 467, 543, 603, 614 (list; graph; refs; listen; history; text; internal format)
 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. LINKS FORMULA {j: A002110(j)*2^A103782(j)-1 in A001359}. 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: isA177064 := proc(n) A002110(n)*2^A103782(n)-1 ; isA001359(%) ; 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 Cf. A001359, A103782, A103783, A176994, A177031. Sequence in context: A323289 A065885 A274331 * A092233 A115895 A116017 Adjacent sequences:  A177061 A177062 A177063 * A177065 A177066 A177067 KEYWORD nonn AUTHOR Pierre CAMI, Dec 09 2010 STATUS approved

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Last modified August 11 09:56 EDT 2020. Contains 336423 sequences. (Running on oeis4.)