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%I #37 Sep 08 2022 08:46:21
%S 8,14,20,24,26,32,34,38,44,48,50,54,56,62,64,68,74,76,80,84,86,90,92,
%T 94,98,104,110,114,116,118,120,122,124,128,132,134,140,142,144,146,
%U 152,154,158,160,164,168,170,174,176,182,184,186,188,194,200,202,204,206
%N Even numbers k such that k! is divisible by k*(k+1)/2.
%C Even terms in A060462.
%C And A071904 are the successors of a(n).
%C Even numbers that are not a prime - 1. That is, even numbers not in A006093. - _Terry D. Grant_, Oct 31 2020
%D J. D. E. Konhauser et al., Which Way Did The Bicycle Go?, Problem 98, pp. 29; 145-146, MAA Washington DC, 1996.
%D Die WURZEL - Zeitschrift für Mathematik, 53. Jahrgang, Juli 2019, S. 171, WURZEL-Aufgabe 2019-36 von Gerhard Dietel, Regensburg.
%F a(n) = A071904(n) - 1.
%e 8! = 40320 is divisible by 8*9/2 = 36.
%e 14! is divisible by 14*15/2.
%t Complement[Table[2 n, {n, 1, 103}], Table[EulerPhi[Prime[n]], {n, 1, 103}]] (* _Terry D. Grant_, Oct 31 2020 *)
%o (PARI) forcomposite(c=4,10^3,if(c%2==1,print1(c-1,", "))); \\ _Joerg Arndt_, Jul 25 2019
%o (Magma) [k: k in [2..250]|IsEven(k) and Factorial(k) mod Binomial(k+1,2) eq 0]; // _Marius A. Burtea_, Jul 28 2019
%Y Cf. A060462, A071904.
%Y Essentially the same as A186193.
%Y Cf. A006093.
%K nonn
%O 1,1
%A _Gerhard Palme_, Jul 25 2019
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