%I A101948
%S A101948 4,5,8,13,20,4,1,16,49,100,16,1,4,25,64,36,9,0,9,36,64,25,4,1,16,0,0,0,
%T A101948 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
%U A101948 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
%N A101948 For any n >= 0 and b >= 2, let k be the length of the base-b expansion 
               of n and let M(n, b) be the 2 X k matrix whose first row contains 
               the first k primes in descending order and whose second row contains 
               the base-b expansion of n. Let f(n, b) = determinant[transpose(M(n, 
               b))*M(n, b)]. Sequence gives f(n, 5).
%F A101948 For 0 <= x < b, 1 <= y < b, f(x, b) = x^2+4 and f(yb+x, b) = 4*x^2+9*y^2-12*x*y.
%F A101948 For n >= b^2, f(n, b) = 0.
%e A101948 M(21, 5) = [3,2; 4,1], so a(21) = det([3,4; 2,1]*[3,2; 4,1]) = det([25,
               10; 10,5]) = 25.
%t A101948 Generating A(n, b): A[n_Integer, base_Integer]/;base>=2:= {Prime[Range[Length[IntegerDigits[n, 
               base]]1, -1]], IntegerDigits[n, base]} computing the determinant: 
               Det[Transpose[A[n, b]].A[n, b]] then b = 5 and a(n) = Det[Transpose[A[n, 
               5]].A[n, 5]]
%Y A101948 Sequence in context: A061765 A133940 A030978 this_sequence A087475 A019526 
               A145488
%Y A101948 Adjacent sequences: A101945 A101946 A101947 this_sequence A101949 A101950 
               A101951
%K A101948 base,nonn,easy
%O A101948 0,1
%A A101948 Orges Leka (oleka(AT)students.uni-mainz.de), Dec 22 2004
%E A101948 Edited and extended by David Wasserman (dwasserm(AT)earthlink.net), Mar 
               31 2008