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%I #8 Oct 06 2021 17:55:54
%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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