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A099984 Bisection of A007947. 4
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
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
Sequence in context: A286517 A199423 A100029 * A130141 A130142 A130139
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

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Last modified March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)