This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A001747 #51 Nov 29 2024 15:02:51
%S A001747 2,4,6,10,14,22,26,34,38,46,58,62,74,82,86,94,106,118,122,134,142,146,
%T A001747 158,166,178,194,202,206,214,218,226,254,262,274,278,298,302,314,326,
%U A001747 334,346,358,362,382,386,394,398,422,446,454,458,466,478,482,502
%N A001747 2 together with primes multiplied by 2.
%C A001747 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
%C A001747 Sequence gives solutions of sigma(n) - phi(n) = n + tau(n) where tau(n) is the number of divisors of n.
%C A001747 Numbers n such that sigma(n) = 3*(n - phi(n)).
%C A001747 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
%C A001747 Numbers n such that A092673(n) = 2. - _Jon Perry_, Mar 02 2004
%C A001747 Except for initial terms, this sequence = A073582 = A074845 = A077017. Starting with the term 10, they are identical. - _Robert G. Wilson v_, Jun 15 2004
%C A001747 Together with 8 and 16, even numbers n such that n^2 does not divide (n/2)!. - _Arkadiusz Wesolowski_, Jul 16 2011
%C A001747 Twice noncomposite numbers. - _Omar E. Pol_, Jan 30 2012
%H A001747 T. D. Noe, <a href="/A001747/b001747.txt">Table of n, a(n) for n = 1..1000</a>
%F A001747 a(n) = A001043(n) - A001223(n+1), except for initial term.
%F A001747 a(n) = A116366(n-2,n-2) for n>2. - _Reinhard Zumkeller_, Feb 06 2006
%F A001747 A006093(n) = A143201(a(n+1)) for n>1. - _Reinhard Zumkeller_, Aug 12 2008
%F A001747 a(n) = 2*A008578(n). - _Omar E. Pol_, Jan 30 2012, and _Reinhard Zumkeller_, Feb 16 2012
%t A001747 Join[{2},2*Prime[Range[60]]] (* _Harvey P. Dale_, Jul 23 2013 *)
%o A001747 (PARI) print1(2);forprime(p=2,97,print1(", "2*p)) \\ _Charles R Greathouse IV_, Jan 31 2012
%o A001747 (Magma) [2] cat [2*NthPrime(n): n in [1..60]]; // _G. C. Greubel_, May 18 2019
%o A001747 (Sage) [2]+[2*nth_prime(n) for n in (1..60)] # _G. C. Greubel_, May 18 2019
%o A001747 (GAP) Concatenation([2], List([1..60], n-> 2*Primes[n])); # _G. C. Greubel_, May 18 2019
%Y A001747 Cf. A060679, A009530, A098764.
%Y A001747 Equals {2} UNION {A100484}.
%K A001747 nonn,easy,nice
%O A001747 1,1
%A A001747 _N. J. A. Sloane_