login
Concatenation of all numbers less than or equal to n other than the phi(n) numbers relatively prime to n.
1

%I #7 Nov 09 2019 16:26:52

%S 1,2,3,24,5,2346,7,2468,369,2456810,11,2346891012,13,24678101214,

%T 3569101215,246810121416,17,234689101214151618,19,2456810121415161820,

%U 36791214151821,24681011121416182022,23,23468910121415161820212224,510152025,246810121314161820222426

%N Concatenation of all numbers less than or equal to n other than the phi(n) numbers relatively prime to n.

%C a(1) = 1 as the number itself is to be included. a(p) = p if p is a prime (by definition).

%H Andrew Howroyd, <a href="/A061098/b061098.txt">Table of n, a(n) for n = 1..100</a>

%e a(6) = 2346, as 2,3,4,6 are not coprime to 6 and 1 and 5 are coprime to 6.

%o (PARI) a(n)={if(n==1, 1, fromdigits(concat([digits(k) | k<-[1..n], gcd(k,n)>1])))} \\ _Andrew Howroyd_, Nov 09 2019

%Y Cf. A000010.

%K nonn,base

%O 1,2

%A _Amarnath Murthy_, Apr 19 2001

%E Offset corrected and terms a(14) and beyond from _Andrew Howroyd_, Nov 09 2019