A322924 Sum of n-th Bell number and n-th Bell number written backwards.

2, 2, 4, 10, 66, 77, 505, 1655, 4554, 95259, 695486, 754446, 12166721, 101089109, 414897413, 6841551376, 84604250548, 123761716632, 1633685476445, 13337764677442, 79077443378087, 632521435125225, 7744164113623377, 108500061705109490, 1428467362263664833

Offset: 0

Author

Vincenzo Librandi, Mar 12 2019

Keywords

• nonn
• base
• easy

Comments

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

Examples

			a(4) = 66 because Bell(4) = 15 and 15 + 51 = 66.
a(5) = 77 because Bell(5) = 52 and 52 + 25 = 77.
		

Links

• Robert Israel, Table of n, a(n) for n = 0..500

Crossrefs

Cf. A000110, A004098, A051131, A302092.

Programs

Magma

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

Maple

g:= proc(n) local L,i;
L:= convert(n,base,10);
n + add(L[-i]*10^(i-1),i=1..nops(L))
end proc:
map(g @ combinat:-bell, [$0..30]); # Robert Israel, Mar 13 2019

Mathematica

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

Formula

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