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 A161009 Tribonacci left-bounded rhombic triangle. 1
 1, 1, 1, 3, 2, 1, 7, 7, 3, 1, 18, 20, 12, 4, 1, 48, 59, 40, 18, 5, 1, 132, 174, 132, 68, 25, 6, 1, 372, 517, 426, 247, 105, 33, 7, 1, 1069, 1548, 1362, 864, 415, 152, 42, 8, 1, 3121, 4670, 4332, 2956, 1561, 648, 210, 52, 9, 1, 9232, 14188, 13746, 9960, 5685, 2604, 959, 280 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 REFERENCES Sheng-Liang Yang et al., The Pascal rhombus and Riordan arrays, Fib. Q., 56:4 (2018), 337-347. See Fig. 4. LINKS FORMULA Riordan array ((1/(1-x-x^2-x^2))*c((x/(1-x-x^2-x^3))^2),(x/(1-x-x^2-x^2))*c((x/(1-x-x^2-x^3))^2)). T(n, m) = T'(n-1, m-1)+T'(n-1,m+1)+T'(n-1, m)+T'(n-2, m)+T'(n-3,m), where T'(n, m) = T(n, m) for n >= 0 and 0< = m< = n and T'(n, m) = 0 otherwise. EXAMPLE Triangle begins 1, 1, 1, 3, 2, 1, 7, 7, 3, 1, 18, 20, 12, 4, 1, 48, 59, 40, 18, 5, 1, 132, 174, 132, 68, 25, 6, 1, 372, 517, 426, 247, 105, 33, 7, 1 We have, for instance, 132=59+18+40+12+3. MAPLE A161009 := proc(n, m)     option remember;     if m < 0 or m >n then         0;     elif n = m then         1;     else         procname(n-1, m-1)+procname(n-1, m+1)+procname(n-1, m)+procname(n-2, m)+procname(n-3, m) ;     end if; end proc: # R. J. Mathar, Mar 09 2016 CROSSREFS Sequence in context: A277919 A094531 A274293 * A111960 A130462 A059380 Adjacent sequences:  A161006 A161007 A161008 * A161010 A161011 A161012 KEYWORD easy,nonn,tabl AUTHOR Paul Barry, Jun 02 2009 STATUS approved

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Last modified December 16 00:33 EST 2019. Contains 330013 sequences. (Running on oeis4.)