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

Author

Cino Hilliard, Jul 24 2003

Keywords

• easy
• nonn
• base
• changed

Comments

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

Examples

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

Links

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

Crossrefs

Cf. A000796, A086639.

Programs

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 *)

Formula

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

Extensions

Edited by Robert G. Wilson v, Jul 26 2003