OFFSET
0,1
LINKS
Eric Weisstein's World of Mathematics, Concatenation
FORMULA
a(n) = (2n+1)*10^b + n^2 + n, where b is length of n^2 + n.
EXAMPLE
For n = 0: n+1 = 1; 0+1 is 1 and 0*1 is 0. So concatenate to a(0) = 10.
For n = 1: n+1 = 2; 1+2 is 3 and 1*2 is 2. So a(1) = 32.
For n = 10: n+1 = 11; 10+11 is 21 and 10*11 is 110. So a(10) = 21110.
MATHEMATICA
Table[(2n+1)*10^Length[IntegerDigits[n^2+n]]+n^2+n, {n, 0, 38}] (* Stefano Spezia, Jan 29 2021 *)
PROG
(Python)
def concatenate(n):
return (2*n+1)*10**len(str(n**2+n))+ n**2+n
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Ercan Isik, Jan 27 2021
EXTENSIONS
More terms from Stefano Spezia, Jan 29 2021
STATUS
approved