A099984 Bisection of A007947.

1, 3, 5, 7, 3, 11, 13, 15, 17, 19, 21, 23, 5, 3, 29, 31, 33, 35, 37, 39, 41, 43, 15, 47, 7, 51, 53, 55, 57, 59, 61, 21, 65, 67, 69, 71, 73, 15, 77, 79, 3, 83, 85, 87, 89, 91, 93, 95, 97, 33, 101, 103, 105, 107, 109, 111, 113, 115, 39, 119, 11, 123, 5, 127, 129, 131, 133, 15, 137

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Formula

From Amiram Eldar, Nov 19 2022: (Start)

a(n) = A007947(2*n-1).

Sum_{k=1..n} a(k) ~ c * n^2, where c = (6/5) * Product_{p prime} (1 - 1/(p*(p+1))) = (6/5) * A065463 = 0.8453306... . (End)

Maple

with(numtheory): A007947 := proc(n) local i, t1, t2; t1 :=ifactors(n)[2]; t2 := mul(t1[i][1], i=1..nops(t1)); end: seq(A007947(2*n-1), n=1..78); # Emeric Deutsch, Dec 15 2004

Mathematica

a[n_] := Times @@ (First /@ FactorInteger[2*n-1]); Array[a, 100]  (* Amiram Eldar, Nov 19 2022*)

Prog

(PARI) a(n) = factorback(factorint(2*n-1)[, 1]); \\ Amiram Eldar, Nov 19 2022

Crossrefs

Cf. A007947, A065463, A099985.

Sequence in context: A377865 A199423 A100029 * A130141 A130142 A130139

Adjacent sequences: A099981 A099982 A099983 * A099985 A099986 A099987

Keyword

nonn,easy

Author

N. J. A. Sloane, Nov 19 2004

Extensions

More terms from Emeric Deutsch, Dec 15 2004

Offset corrected by Amiram Eldar, Nov 19 2022

Status

approved