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A100484 The primes doubled. 191
4, 6, 10, 14, 22, 26, 34, 38, 46, 58, 62, 74, 82, 86, 94, 106, 118, 122, 134, 142, 146, 158, 166, 178, 194, 202, 206, 214, 218, 226, 254, 262, 274, 278, 298, 302, 314, 326, 334, 346, 358, 362, 382, 386, 394, 398, 422, 446, 454, 458, 466, 478, 482, 502, 514, 526 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Even semiprimes.
Essentially the same as A001747.
Right edge of the triangle in A065342. - Reinhard Zumkeller, Jan 30 2012
A253046(a(n)) > a(n). - Reinhard Zumkeller, Dec 26 2014
Apart from first term, these are the tau2-primes as defined in [Anderson, Frazier] and [Lanterman]. - Michel Marcus, May 15 2019
For every positive integer b and each m in this sequence b^(m-1) == b (mod m). - Florian Baur, Nov 26 2021
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
D. D. Anderson and Andrea M. Frazier, On a general theory of factorization in integral domains, Rocky Mountain J. Math., Volume 41, Number 3 (2011), 663-705. See pp. 698, 699, 702.
James Lanterman, Irreducibles in the Integers modulo n, arXiv:1210.2991 [math.NT], 2012.
Eric Weisstein's World of Mathematics, Semiprime
FORMULA
a(n) = 2 * A000040(n).
a(n) = A001747(n+1).
n>1: A000005(a(n)) = 4; A000203(a(n)) = 3*A008864(n); A000010(a(n)) = A006093(n); intersection of A001358 and A005843.
a(n) = A116366(n-1, n-1) for n>1. - Reinhard Zumkeller, Feb 06 2006
a(n) = A077017(n+1), n>1. - R. J. Mathar, Sep 02 2008
A078834(a(n)) = A000040(n). - Reinhard Zumkeller, Sep 19 2011
a(n) = A087112(n, 1). - Reinhard Zumkeller, Nov 25 2012
A000203(a(n)) = 3*n/2 + 3, n > 1. - Wesley Ivan Hurt, Sep 07 2013
MAPLE
A100484:=n->2*ithprime(n); seq(A100484(n), n=1..70); # Wesley Ivan Hurt, Mar 27 2014
MATHEMATICA
2*Prime[Range[70]] (* Vladimir Joseph Stephan Orlovsky, Apr 29 2008 *)
PROG
(PARI) 2*primes(70) \\ Charles R Greathouse IV, Aug 21 2011
(Haskell)
a100484 n = a100484_list !! (n-1)
a100484_list = map (* 2) a000040_list
-- Reinhard Zumkeller, Jan 31 2012
(Magma) [2*p: p in PrimesUpTo(350)]; // Vincenzo Librandi, Mar 27 2014
(GAP) 2*Filtered([1..300], IsPrime); # Muniru A Asiru, Oct 05 2018
(GAP) List([1..70], n-> 2*Primes[n]) # G. C. Greubel, May 18 2019
(Sage) [2*nth_prime(n) for n in (1..70)] # G. C. Greubel, May 18 2019
CROSSREFS
Subsequence of A091376.
Row 3 of A286625, column 3 of A286623.
Sequence in context: A243428 A091376 A363134 * A076924 A103801 A141247
KEYWORD
nonn,easy
AUTHOR
Reinhard Zumkeller, Nov 22 2004
EXTENSIONS
Simpler definition.
STATUS
approved

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Last modified February 27 08:19 EST 2024. Contains 370367 sequences. (Running on oeis4.)