OFFSET
1,2
REFERENCES
M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia. [See A056391 for pdf file of Chap. 2]
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..1275
FORMULA
T(n,k) = Sum_{d | n} mu(n/d) * k^(ceiling(d/2)).
EXAMPLE
Table starts:
1 2 3 4 5 6 7 8 9 10 ...
0 0 0 0 0 0 0 0 0 0 ...
0 2 6 12 20 30 42 56 72 90 ...
0 2 6 12 20 30 42 56 72 90 ...
0 6 24 60 120 210 336 504 720 990 ...
0 4 18 48 100 180 294 448 648 900 ...
0 14 78 252 620 1290 2394 4088 6552 9990 ...
0 12 72 240 600 1260 2352 4032 6480 9900 ...
0 28 234 1008 3100 7740 16758 32704 58968 99900 ...
0 24 216 960 3000 7560 16464 32256 58320 99000 ...
...
Row 4 includes palindromes of the form abba but excludes those of the form aaaa, so T(4,k) is k*(k-1).
Row 6 includes palindromes of the forms aabbaa, abbbba, abccba but excludes those of the forms aaaaaa, abaaba, so T(6,k) is 2*k*(k-1) + k*(k-1)*(k-2).
MATHEMATICA
T[n_, k_] := DivisorSum[n, MoebiusMu[n/#]*k^Ceiling[#/2]&]; Table[T[n-k+1, k], {n, 1, 12}, {k, n, 1, -1}] // Flatten (* Jean-François Alcover, Jun 05 2017 *)
PROG
(PARI)
a(n, k) = sumdiv(n, d, moebius(n/d) * k^(ceil(d/2)));
for(n=1, 10, for(k=1, 10, print1( a(n, k), ", "); ); print(); )
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Andrew Howroyd, Apr 03 2017
STATUS
approved