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

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, 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, 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

Offset

1,1

Comments

Select digits from decimal expansion of Pi corresponding to triangular number indices. - Harvey P. Dale, Oct 15 2011

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

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

Example

Triangle is:
  3
  14
  159
  2653
  58979
  323846
  2643383
  27950288
  419716939
  9375105820

Mathematica

pi = RealDigits[Pi, 10, 5565][[1]]; Table[ pi[[n(n + 1)/2]], {n, 1, 105}]
With[{nn=110}, RealDigits[Pi, 10, (nn(nn+1))/2][[1]][[Accumulate[ Range[ nn]]]]] (* Harvey P. Dale, Oct 15 2011 *)
Module[{nn=110}, Last[#]&/@TakeList[RealDigits[Pi, 10, (nn(nn+1))/2][[1]], Range[ nn]]] (* Harvey P. Dale, Oct 02 2022 *)

Crossrefs

Cf. A000796, A086639.

Sequence in context: A122791 A011429 A225409 * A011292 A021745 A190285

Adjacent sequences: A083434 A083435 A083436 * A083438 A083439 A083440

Keyword

easy,nonn,base

Author

Cino Hilliard, Jul 24 2003

Extensions

Edited by Robert G. Wilson v, Jul 26 2003

Status

approved