A083437 - OEIS

%I #13 Oct 02 2022 16:22:37

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

%C Select digits from decimal expansion of Pi corresponding to triangular number indices.  [From Harvey P. Dale, Oct 15 2011]

%H Harvey P. Dale, <a href="/A083437/b083437.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n)=A000796(2-n(n+1)/2). - M. F. Hasler, Oct 20 2011

%e Triangle is

%e 3

%e 14

%e 159

%e 2653

%e 58979

%e 323846

%e 2643383

%e 27950288

%e 419716939

%e 9375105820

%t pi = RealDigits[Pi, 10, 5565][[1]]; Table[ pi[[n(n + 1)/2]], {n, 1, 105}]

%t With[{nn=110},RealDigits[Pi,10,(nn(nn+1))/2][[1]][[Accumulate[ Range[ nn]]]]] (* _Harvey P. Dale_, Oct 15 2011 *)

%t Module[{nn=110},Last[#]&/@TakeList[RealDigits[Pi,10,(nn(nn+1))/2][[1]],Range[ nn]]] (* _Harvey P. Dale_, Oct 02 2022 *)

%Y Cf. A000796, A086639.

%K easy,nonn,base

%O 1,1

%A _Cino Hilliard_, Jul 24 2003

%E Edited by _Robert G. Wilson v_, Jul 26 2003