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A099965 First column (also row sums) of triangle in A099964. 4
1, 1, 1, 2, 3, 8, 17, 39, 126, 352, 1026, 2943, 11429, 39138, 138903, 486490, 1711141, 7720713, 31383260, 131236182, 543056039, 2254646235, 9349845765, 48137959377, 226341090088, 1090094720010, 5203693239201, 24909594299924 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 0..750

MAPLE

with(linalg):rev:=proc(a) local n, p; n:=vectdim(a): p:=i->a[n+1-i]: vector(n, p) end: ps:=proc(a) local n, q; n:=vectdim(a): q:=i->sum(a[j], j=1..i): vector(n, q) end: pss:=proc(a) local n, q; n:=vectdim(a): q:=proc(i) if i<=n then sum(a[j], j=1..i) else sum(a[j], j=1..n) fi end: vector(n+1, q) end: tr:={seq(n*(n+1)/2, n=1..30)}: R[0]:=vector(1, 1): for n from 1 to 31 do if member(n, tr)=false then R[n]:=ps(rev(R[n-1])) else R[n]:=pss(rev(R[n-1])) fi od: seq(R[n][1], n=0..31); # Emeric Deutsch, Nov 16 2004

MATHEMATICA

triQ[n_] := Reduce[n == k (k + 1)/2, k, Integers] =!= False; row[0] = {1}; row[1] = {1, 1}; row[n_] := row[n] = (ro = Accumulate[Reverse[row[n-1]]]; If[triQ[n], Append[ro, Last[ro]], ro]); Table[row[n][[1]], {n, 0, 27}] (* Jean-Fran├žois Alcover, Feb 10 2018 *)

PROG

(Haskell)

a099965 = flip a099964 0

a099965_list = map head a099964_tabf

-- Reinhard Zumkeller, May 02 2012

CROSSREFS

Cf. A099964.

Sequence in context: A256169 A298405 A219788 * A319566 A294450 A292852

Adjacent sequences:  A099962 A099963 A099964 * A099966 A099967 A099968

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Nov 13 2004, following a suggestion made by Douglas G. Rogers, Mar 10 2003

EXTENSIONS

More terms from Emeric Deutsch, Nov 16 2004

STATUS

approved

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Last modified July 15 20:24 EDT 2019. Contains 325056 sequences. (Running on oeis4.)