A322924 - OEIS

%I #14 Sep 08 2022 08:46:23

%S 2,2,4,10,66,77,505,1655,4554,95259,695486,754446,12166721,101089109,

%T 414897413,6841551376,84604250548,123761716632,1633685476445,

%U 13337764677442,79077443378087,632521435125225,7744164113623377,108500061705109490,1428467362263664833

%N Sum of n-th Bell number and n-th Bell number written backwards.

%C After 2, the next prime Bell number is a(110), which has 131 digits.

%H Robert Israel, <a href="/A322924/b322924.txt">Table of n, a(n) for n = 0..500</a>

%F a(n) = A000110(n) + A004098(n).

%e a(4) = 66 because Bell(4) = 15 and 15 + 51 = 66.

%e a(5) = 77 because Bell(5) = 52 and 52 + 25 = 77.

%p g:= proc(n) local L,i;

%p L:= convert(n,base,10);

%p n + add(L[-i]*10^(i-1),i=1..nops(L))

%p end proc:

%p map(g @ combinat:-bell, [$0..30]); # _Robert Israel_, Mar 13 2019

%t BellB[#] + FromDigits[Reverse[IntegerDigits[BellB[#]]]]&/@Range[0, 30]

%o (Magma) [Bell(n) + Seqint(Reverse(Intseq(Bell(n)))): n in [0..30]];

%Y Cf. A000110, A004098, A051131, A302092.

%K nonn,base,easy

%O 0,1

%A _Vincenzo Librandi_, Mar 12 2019