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A023528 Exponent of 2 in prime factorization of prime(n)*prime(n-1) + 1. 1
0, 0, 4, 2, 1, 4, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 3, 4, 3, 1, 6, 3, 1, 2, 1, 1, 2, 1, 4, 1, 4, 1, 2, 2, 3, 2, 2, 3, 1, 2, 3, 4, 2, 12, 1, 2, 1, 1, 1, 4, 1, 3, 8, 2, 2, 3, 2, 2, 2, 1, 2, 3, 5, 1, 6, 1, 5, 2, 2, 4, 1, 3, 1, 2, 3, 1, 2, 1, 1, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Assumes the not generally accepted convention prime(0) = 1. - Michel Marcus, Jun 06 2019

LINKS

Marius A. Burtea, Table of n, a(n) for n = 1..6001

FORMULA

a(n) = A007814(A023523(n)). - Michel Marcus, Jun 06 2019

MATHEMATICA

Join[{0}, FactorInteger[#][[1, 2]]&/@(Times@@@Partition[Prime[Range[ 80]], 2, 1]+1)] (* Harvey P. Dale, Dec 25 2011 *)

PROG

(PARI) p(n) = if (n==0, 1, prime(n));

a(n) = valuation(p(n)*p(n-1) + 1, 2); \\ Michel Marcus, Jun 06 2019

(MAGMA) p:=PrimesUpTo(10000); sol:=[]; sol[1]:=0; for n in [2..80] do sol[n]:=Valuation(1+p[n]*p[n-1], 2); end for; sol; // Marius A. Burtea, Jun 06 2019

CROSSREFS

Cf. A007814, A023523.

Sequence in context: A071406 A010311 A326485 * A236308 A105698 A105699

Adjacent sequences:  A023525 A023526 A023527 * A023529 A023530 A023531

KEYWORD

nonn

AUTHOR

Clark Kimberling

EXTENSIONS

a(1)=a(2)=0 corrected by Sean A. Irvine, Jun 05 2019

STATUS

approved

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Last modified February 25 04:32 EST 2020. Contains 332217 sequences. (Running on oeis4.)