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A077003 a(n)= index of triangular number A077002(n). 1

%I

%S 1,1,1,2,4,9,22,59,167,501,1585,5258,18215,65676,245738,951740,

%T 3806961,15696503,66594623,290279233,1298168196,5948954024,

%U 27903067710,133818411722,655573653819,3277868269096,16713914267109,86848046111951

%N a(n)= index of triangular number A077002(n).

%p a[1] := 1:b[1] := 1:for n from 2 to 100 do a[n] := floor(evalf(-1/2+1/2*sqrt(1+8*(n-1)*a[n-1])+1/10^50,300)):b[n] := a[n]:a[n] := a[n]*(a[n]+1)/2:od:seq(b[l],l=1..100);

%Y Cf. A077002.

%K nonn

%O 1,4

%A _Amarnath Murthy_, Oct 26 2002

%E More terms from _Sascha Kurz_, Jan 26 2003

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Last modified July 15 16:29 EDT 2019. Contains 325049 sequences. (Running on oeis4.)