A258080 a(n) = ((n concatenated with n+1) + (n+1 concatenated with n)) mod n*(n+1).

1, 1, 5, 19, 1, 17, 53, 43, 29, 31, 79, 29, 179, 199, 11, 69, 169, 317, 139, 361, 185, 497, 331, 149, 601, 439, 263, 73, 739, 581, 411, 229, 35, 1019, 871, 713, 545, 367, 179, 1621, 1495, 1361, 1219, 1069, 911, 745, 571, 389, 199, 1, 2447, 2337, 2221, 2099

Offset: 1

Author

Vladimir Shevelev, May 19 2015

Keywords

• nonn
• base

Links

• Peter J. C. Moses, Table of n, a(n) for n = 1..2000

Crossrefs

Cf. A001704 (concatenation {n,n+1}).

Programs

Mathematica

Map[Mod[FromDigits[Flatten[{#1,#2}]]+FromDigits[Flatten[{#2,#1}]]&[IntegerDigits[#+1],IntegerDigits[#]],# (#+1)]&,Range[100]] (*Peter J. C. Moses, May 19 2015*)
Mod[(#[[1]]*10^IntegerLength[#[[2]]]+#[[2]])+(#[[2]]*10^IntegerLength[#[[1]]]+#[[1]]),Times@@#]&/@Partition[Range[60],2,1] (* Harvey P. Dale, Jul 21 2025 *)

PARI

a(n) = (eval(concat(Str(n), Str(n+1))) + eval(concat(Str(n+1), Str(n)))) % (n*(n+1)); \\ Michel Marcus, Jun 04 2015

Extensions

More terms from Peter J. C. Moses, May 19 2015