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A083437 Write decimal expansion of Pi in triangular form; sequence gives right edge.

%I A083437 #17 Sep 01 2025 17:24:19
%S A083437 3,4,9,3,9,6,3,8,9,0,0,0,5,4,4,2,8,3,8,7,3,5,2,7,1,6,6,7,3,4,1,9,7,9,
%T A083437 4,5,2,7,5,2,3,9,1,0,8,1,3,0,0,4,6,3,2,2,1,9,6,6,5,6,2,6,6,0,9,4,6,1,
%U A083437 6,3,4,8,4,3,1,8,6,2,2,5,7,2,5,5,9,5,9,6,5,1,6,5,5,3,1,6,8,6,3,2,2,9,7,1,6
%N A083437 Write decimal expansion of Pi in triangular form; sequence gives right edge.
%C A083437 Select digits from decimal expansion of Pi corresponding to triangular number indices. - _Harvey P. Dale_, Oct 15 2011
%H A083437 Harvey P. Dale, <a href="/A083437/b083437.txt">Table of n, a(n) for n = 1..1000</a>
%F A083437 a(n) = A000796(2-n*(n+1)/2). - _M. F. Hasler_, Oct 20 2011
%e A083437 Triangle is:
%e A083437   3
%e A083437   14
%e A083437   159
%e A083437   2653
%e A083437   58979
%e A083437   323846
%e A083437   2643383
%e A083437   27950288
%e A083437   419716939
%e A083437   9375105820
%t A083437 pi = RealDigits[Pi, 10, 5565][[1]]; Table[ pi[[n(n + 1)/2]], {n, 1, 105}]
%t A083437 With[{nn=110},RealDigits[Pi,10,(nn(nn+1))/2][[1]][[Accumulate[ Range[ nn]]]]] (* _Harvey P. Dale_, Oct 15 2011 *)
%t A083437 Module[{nn=110},Last[#]&/@TakeList[RealDigits[Pi,10,(nn(nn+1))/2][[1]],Range[ nn]]] (* _Harvey P. Dale_, Oct 02 2022 *)
%Y A083437 Cf. A000796, A086639.
%K A083437 easy,nonn,base,changed
%O A083437 1,1
%A A083437 _Cino Hilliard_, Jul 24 2003
%E A083437 Edited by _Robert G. Wilson v_, Jul 26 2003