A153518 Triangular T(n,k) = T(n-1, k) + T(n-1, k-1) + 5*T(n-2, k-1), read by rows.

2, 5, 5, 2, 46, 2, 2, 123, 123, 2, 2, 135, 476, 135, 2, 2, 147, 1226, 1226, 147, 2, 2, 159, 2048, 4832, 2048, 159, 2, 2, 171, 2942, 13010, 13010, 2942, 171, 2, 2, 183, 3908, 26192, 50180, 26192, 3908, 183, 2, 2, 195, 4946, 44810, 141422, 141422, 44810, 4946, 195, 2

Offset: 1

Author

Roger L. Bagula, Dec 28 2008

Keywords

• nonn
• tabl
• easy
• less

Examples

			Triangle begins as:
  2;
  5,   5;
  2,  46,    2;
  2, 123,  123,     2;
  2, 135,  476,   135,      2;
  2, 147, 1226,  1226,    147,      2;
  2, 159, 2048,  4832,   2048,    159,     2;
  2, 171, 2942, 13010,  13010,   2942,   171,    2;
  2, 183, 3908, 26192,  50180,  26192,  3908,  183,   2;
  2, 195, 4946, 44810, 141422, 141422, 44810, 4946, 195, 2;
		

Links

• G. C. Greubel, Rows n = 1..50 of the triangle, flattened

Crossrefs

Sequences with variable (p,q,j): A153516 (0,1,2), this sequences (0,1,3), A153520 (0,1,4), A153521 (0,1,5), A153648 (1,0,3), A153649 (1,1,4), A153650 (1,4,5), A153651 (1,5,6), A153652 (2,1,7), A153653 (2,1,8), A153654 (2,1,9), A153655 (2,1,10), A153656 (2,3,9), A153657 (2,7,10).

Cf. A123011.

Programs

Magma

f:= func< n,j | Round(((3-(-1)^n)/2)*NthPrime(j)^(n-1) - 2^((3-(-1)^n)/2)) >;
function T(n,k,p,q,j)
  if n eq 2 then return NthPrime(j);
  elif (n eq 3 and k eq 2 or n eq 4 and k eq 2 or n eq 4 and k eq 3) then return f(n,j);
  elif (k eq 1 or k eq n) then return 2;
  else return T(n-1,k,p,q,j) + T(n-1,k-1,p,q,j) + (p*j+q)*NthPrime(j)*T(n-2,k-1,p,q,j);
  end if; return T;
end function;
[T(n,k,0,1,3): k in [1..n], n in [1..12]]; // G. C. Greubel, Mar 04 2021

Maple

A153518 := proc(n,k) option remember ; if n =1 then 2; elif n = 2 then 5; elif k=1 or k=n then 2; elif n = 3 then 46 ; elif n = 4 then 123 ; else procname(n-1,k-1)+procname(n-1,k)+5*procname(n-2,k-1) ; end: end: for n from 1 to 13 do for k from 1 to n do printf("%d,",A153518(n,k)) ; od: od: # R. J. Mathar, Jan 22 2009

Mathematica

T[n_, k_, p_, q_, j_]:= T[n,k,p,q,j]= If[n==2, Prime[j], If[n==3 && k==2 || n==4 && 2<=k<=3, ((3-(-1)^n)/2)*Prime[j]^(n-1) -2^((3-(-1)^n)/2), If[k==1 || k==n, 2, T[n-1,k,p,q,j] + T[n-1,k-1,p,q,j] + (p*j+q)*Prime[j]*T[n-2,k-1,p,q,j] ]]];
Table[T[n,k,0,1,3], {n,12}, {k,n}]//Flatten (* modified by G. C. Greubel, Mar 04 2021 *)

Sage

@CachedFunction
def f(n,j): return ((3-(-1)^n)/2)*nth_prime(j)^(n-1) - 2^((3-(-1)^n)/2)
def T(n,k,p,q,j):
    if (n==2): return nth_prime(j)
    elif (n==3 and k==2 or n==4 and 2<=k<=3): return f(n,j)
    elif (k==1 or k==n): return 2
    else: return T(n-1,k,p,q,j) + T(n-1,k-1,p,q,j) + (p*j+q)*nth_prime(j)*T(n-2,k-1,p,q,j)
flatten([[T(n,k,0,1,3) for k in (1..n)] for n in (1..12)]) # G. C. Greubel, Mar 04 2021

Formula

T(n,k) = T(n-1, k) + T(n-1, k-1) + 5*T(n-2, k-1).

Recurrence row sums: s(n) = 2*s(n-1) + 5*s(n-2), n > 4, with s(1) = 2, s(2) = 10, s(3) = 50, s(4) = 250. - R. J. Mathar, Jan 22 2009

From G. C. Greubel, Mar 04 2021: (Start)

T(n,k,p,q,j) = T(n-1,k,p,q,j) + T(n-1,k-1,p,q,j) + (p*j+q)*prime(j)*T(n-2,k-1,p,q,j) with T(2,k,p,q,j) = prime(j), T(3,2,p,q,j) = 2*prime(j)^2 -4, T(4,2,p,q, j) = T(4,3,p,q,j) = prime(j)^2 -2, T(n,1,p,q,j) = T(n,n,p,q,j) = 2 and (p, q, j) = (0,1,3).

Sum_{k=0..n} T(n,k,0,1,3) = 4*(-5)^n*[n<2] + 50*(i*sqrt(5))^(n-2)*(ChebyshevU(n-2, -i/sqrt(5)) - (3*i/sqrt(5))*ChebyshevU(n-3, -i/sqrt(5))) = 4*(-5)^n*[n<2] + 50*A123011(n-2). (End)

Extensions

More terms from R. J. Mathar, Jan 22 2009

Edited by G. C. Greubel, Mar 04 2021