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A219603 a(n) = prime(n) * prime(2*n-1). 4
4, 15, 55, 119, 253, 403, 697, 893, 1357, 1943, 2263, 3071, 3977, 4429, 5123, 6731, 8083, 9089, 10519, 11857, 13067, 15089, 16351, 18779, 22019, 23533, 24823, 27499, 29321, 31301, 35941, 40217, 42881, 46009, 51703, 53303, 57619, 61777, 64963, 69373, 75001 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A020639(a(n)) = A000040(n); A006530(a(n)) = A031368(n);

a(n) is central term of row 2n-1 of semiprimes triangle (A087112).

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A000040(n) * A031368(n).

PROG

(Haskell)

a219603 n = a000040 n * a031368 n

(PARI) a(n)=prime(n) * prime(2*n-1) \\ Charles R Greathouse IV, Feb 07 2017

CROSSREFS

Subsequence of A001358.

Cf. A006094.

Sequence in context: A001559 A002311 A102349 * A268164 A291029 A126932

Adjacent sequences:  A219600 A219601 A219602 * A219604 A219605 A219606

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Nov 25 2012

STATUS

approved

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Last modified October 15 12:31 EDT 2019. Contains 328026 sequences. (Running on oeis4.)