login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS").
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A001748 3 * primes. 31
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 24 07:53 EST 2020. Contains 338607 sequences. (Running on oeis4.)