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

0,1

Comments

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

Links

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

Formula

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

Example

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

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]

Prog

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

Crossrefs

Cf. A000110, A004098, A051131, A302092.

Sequence in context: A034165 A006181 A366425 * A173100 A092635 A270549

Adjacent sequences: A322921 A322922 A322923 * A322925 A322926 A322927

Keyword

nonn,base,easy

Author

Vincenzo Librandi, Mar 12 2019

Status

approved