A261080 Semiprimes p*q for which p and q are successive primes and their binary representations differ from each other in one bit position only.

6, 35, 323, 437, 899, 1763, 2021, 4757, 9797, 10403, 19043, 22499, 27221, 38021, 39203, 72899, 79523, 95477, 99221, 131753, 145157, 154433, 164009, 205193, 210677, 213443, 250997, 272483, 324899, 381923, 412163, 416021, 455621, 549077, 557993, 594437, 656099, 675683, 736163, 741317, 777923, 783221, 826277, 870473, 881717, 974153, 1022117, 1102499, 1127843, 1238753

Offset

1,1

Comments

Numbers n for which A260737(n) = A261079(n) = 1.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

a(n) = A205511(n) * A205302(n).

Example

6 is included as 6 = 2*3, 2 and 3 are successive primes, and 2 (in binary "10") and 3 (in binary "11") differ by only one bit from each other.

Mathematica

brdQ[{a_, b_}]:=Module[{c=IntegerDigits[a, 2], d=IntegerDigits[b, 2]}, Length[ c] == Length[d]&&Count[Total/@Transpose[{c, d}], 1]==1]; Times@@@ Select[ Partition[Prime[Range[200]], 2, 1], brdQ] (* Harvey P. Dale, Jan 29 2016 *)

Prog

(Scheme, two variants, the other one requiring Antti Karttunen's IntSeq-library)
(define (A261080 n) (* (A205302 n) (A205511 n)))
(define A261080 (MATCHING-POS 1 1 (lambda (n) (and (= 1 (A260737 n)) (= 1 (A261079 n))))))

Crossrefs

Cf. A205302, A205511, A260737, A261079.

Intersection of A006094 and A261077.

Sequence in context: A357037 A356460 A261073 * A356494 A291595 A268139

Adjacent sequences: A261077 A261078 A261079 * A261081 A261082 A261083

Keyword

nonn

Author

Antti Karttunen, Sep 23 2015

Status

approved