login
Triangular number index of A077206(n).
1

%I #13 Nov 16 2024 17:29:55

%S 1,5,32,126,141,447,4001,4472,40001,44721,141421,447214,3162278,

%T 4472136,34641016,109544512,400000001,447213596,3464101616,

%U 10954451150,31622776602,77459666925,316227766017,774596669241,1414213562373,4472135955001,14142135623731

%N Triangular number index of A077206(n).

%o (PARI)

%o {rT(m) = ceil((sqrt(8*m+1)-1)/2)}

%o {T(n) = (n*(n+1))/2}

%o m=1;for(n=2,50,k=rT((m%10)*10^(n-1));while(T(k)%10==0,k++);m=T(k);print1(" ",k)) \\ _Max Alekseyev_, Feb 15 2005

%Y Cf. A000217, A077206.

%K base,nonn

%O 1,2

%A _Amarnath Murthy_, Nov 02 2002

%E Corrected and extended by _Max Alekseyev_, Feb 15 2005.

%E a(25) and a(26) added by _Robert C. Lyons_, Nov 16 2024.