login
a(1) = 1; a(n+1) = smallest triangular numbers starting with a(n).
0

%I #16 May 12 2023 12:43:38

%S 1,10,105,10585,105858525,10585852585252500,

%T 105858525852525008525250025000000,

%U 10585852585252500852525002500000085252500250000002500000000000000

%N a(1) = 1; a(n+1) = smallest triangular numbers starting with a(n).

%F a(n+1) = floor((sqrt(8*10^floor(log(a(n))/log(10))*a(n)+1)+1)/2)*(floor((sqrt(8*10^floor(log(a(n))/log(10))*a(n)+1)+1)/2)+1)/2. - _Benoit Cloitre_, Feb 25 2002

%o (PARI) /* with 1000 significant digits : */ a(1)=1, a(2)=10 and for n>2 s=10; for(i=1,10,s=floor((sqrt(8*10^floor(log(s)/log(10))*s+1)+1)/2)*(floor((sqrt(8*10^floor(log(s)/log(10))*s+1)+1)/2)+1)/2; print1(s,","); );

%K base,nonn

%O 1,2

%A _Amarnath Murthy_, Feb 19 2002

%E More terms from _Vladeta Jovovic_, Feb 24 2002

%E More terms from _Benoit Cloitre_, Mar 07 2002