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 A114333 #12 Dec 17 2019 05:52:45
%S A114333 2,3,4,5,28,32
%N A114333 Integers K with prime sum of the first K factorials of odd numbers.
%C A114333 k = 6, 7, 8, 22, 27, and 29 yield semiprimes.
%C A114333 The sequence is finite because the sum of the factorials of the first k odd numbers is divisible by 107 for every k >= 53. - _Giovanni Resta_, Jun 14 2016
%F A114333 {a(n)} = {k such that 1! + 3! + ... + (2k-1)! is prime}.
%F A114333 {a(n)} = {k such that Sum_{j=1..k} A000142(A005408(j)) is in A000040}.
%e A114333 a(1) = 2 because 1! + 3! = 7 is prime.
%e A114333 a(2) = 3 because 1! + 3! + 5! = 127 is prime.
%e A114333 a(3) = 4 because 1! + 3! + 5! + 7! = 5167 is prime.
%e A114333 a(5) = 28 because 1! + 3! + 5! + 7! + 9! + 11! + 13! + 15! + 17! + 19! + 21! + 23! + 25! + 27! + 29! + 31! + 33! + 35! + 37! + 39! + 41! + 43! + 45! + 47! + 49! + 51! + 53! + 55! = 12700679788669629845870127416097655693745481645117320232505943379392681647 is prime.
%e A114333 a(6) = 32 because 1! + 3! + ... + (2*32+1)! = 1! + 3! + ... + 63! = 1983116034341975454789449189498620955194254460449807567074683265838922666583379392681647 is prime.
%t A114333 Select[Range[100], PrimeQ[Sum[(2 k - 1)!, {k, #}]] &] (* _Giovanni Resta_, Jun 14 2016 *)
%Y A114333 Cf. A000040, A000142, A005408.
%K A114333 nonn,fini,full
%O A114333 1,1
%A A114333 _Jonathan Vos Post_, Feb 06 2006
%E A114333 Missing a(4) = 5 and keywords fini and full added by _Giovanni Resta_, Jun 14 2016