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A001748 3 * primes. 28
6, 9, 15, 21, 33, 39, 51, 57, 69, 87, 93, 111, 123, 129, 141, 159, 177, 183, 201, 213, 219, 237, 249, 267, 291, 303, 309, 321, 327, 339, 381, 393, 411, 417, 447, 453, 471, 489, 501, 519, 537, 543, 573, 579, 591, 597, 633, 669, 681, 687, 699, 717, 723, 753 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A164023(a(n)) = A164024(a(n)) = A000040(n). - Reinhard Zumkeller, Aug 09 2009

Semiprimes of the form m*k such that m/(k-2)=prime. - Juri-Stepan Gerasimov, May 25 2010

The sum of two distinct terms from sequence A179545. - Odimar Fabeny, Aug 18 2010

Solutions of the differential equation n'=1/3*(n+9), where n' is the arithmetic derivative of n. - Paolo P. Lava, Feb 02 2012

A253046(a(n)) < a(n). - Reinhard Zumkeller, Dec 26 2014

LINKS

Paolo P. Lava, Table of n, a(n) for n = 1..20000

Eric Weisstein's World of Mathematics, Skeleton

FORMULA

a(n) = 3*A000040(n). - Omar E. Pol, Jan 31 2012

MATHEMATICA

Prime[Range[22]]*3 (* Vladimir Joseph Stephan Orlovsky, Apr 29 2008 *)

PROG

(PARI) 3*primes(22) \\ Charles R Greathouse IV, May 19, 2011

(MAGMA) [3*p: p in PrimesUpTo(300)]; // Vincenzo Librandi, Mar 26 2014

(Haskell)

a001748 = (* 3) . a000040  -- Reinhard Zumkeller, Dec 26 2014

CROSSREFS

Subsequence of A001358.

Cf. A179545. - Odimar Fabeny, Aug 18 2010

Cf. A100484, A253046, A164023, A164024, A000040, A253046.

Sequence in context: A164383 A316047 A168544 * A097426 A075278 A316048

Adjacent sequences:  A001745 A001746 A001747 * A001749 A001750 A001751

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified November 19 08:48 EST 2018. Contains 317347 sequences. (Running on oeis4.)