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 A001747 2 together with primes multiplied by 2. 28
 2, 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS When supplemented with 8, may be considered the "even primes", since these are the even numbers n = 2k which are divisible just by 1, 2, k and 2k. - Louis Zuckerman (louis(AT)trapezoid.com), Sep 12 2000 Sequence gives solutions of sigma(n)-phi(n)=n+tau(n) where tau(n) is the number of divisors of n. Numbers n such that sigma(n)=3*(n-phi(n)). Except for 2, orders of non-cyclic groups k (in A060679(n)) such that x^k==1 (mod k) has only 1 solution 2<=x<=k. - Benoit Cloitre, May 10 2002 Numbers n such that A092673(n)=2. - Jon Perry, Mar 02 2004 Except for initial terms, this sequence = A073582 = A074845 = A077017. Starting with the term 10, they are identical. - Robert G. Wilson v, Jun 15 2004 Together with 8 and 16, even numbers n such that n^2 does not divide (n/2)!. - Arkadiusz Wesolowski, Jul 16 2011 Twice noncomposite numbers. - Omar E. Pol, Jan 30 2012 LINKS T. D. Noe, Table of n, a(n) for n = 1..1000 FORMULA a(n) = A001043(n) - A001223(n+1), except for initial term. a(n) = A116366(n-2,n-2) for n>2. - Reinhard Zumkeller, Feb 06 2006 A006093(n) = A143201(a(n+1)) for n>1. - Reinhard Zumkeller, Aug 12 2008 a(n) = 2*A008578(n). - Omar E. Pol, Jan 30 2012, and Reinhard Zumkeller, Feb 16 2012 MATHEMATICA Join[{2}, 2*Prime[Range[60]]] (* Harvey P. Dale, Jul 23 2013 *) PROG (PARI) print1(2); forprime(p=2, 97, print1(", "2*p)) \\ Charles R Greathouse IV, Jan 31 2012 CROSSREFS Cf. A060679, A009530, A098764. {2} UNION {A100484}. Sequence in context: A237758 A023499 A103445 * A048670 A239951 A077625 Adjacent sequences:  A001744 A001745 A001746 * A001748 A001749 A001750 KEYWORD nonn,easy,nice AUTHOR STATUS approved

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Last modified December 19 03:45 EST 2018. Contains 318245 sequences. (Running on oeis4.)