login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A134574 Array, a(n,k) = total size of all n-length words on a k-letter alphabet, read by antidiagonals. 0

%I #22 Aug 08 2018 04:31:08

%S 1,2,2,3,8,3,4,24,18,4,5,64,81,32,5,6,160,324,192,50,6,7,384,1215,

%T 1024,375,72,7,8,896,4374,5120,2500,648,98,8,9,2048,15309,24576,15625,

%U 5184,1029,128,9,10,4608,52488,114688,93750,38880,9604,1536,162,10

%N Array, a(n,k) = total size of all n-length words on a k-letter alphabet, read by antidiagonals.

%F a(n,k) = n*k^n.

%F O.g.f. (by columns): (k*x)/(-1+k*x)^2.

%F E.g.f. (by columns): k*x*exp(k*x).

%F a(n,k) = Sum[k^n,{j,1,n}] = n*Sum[C(n,m)*(k-1)^m,{m,0,n}]. - _Ross La Haye_, Jan 26 2008

%e a(2,2) = 8 because there are 2^2 = 4 2-length words on a 2 letter alphabet, each of size 2 and 2*4 = 8.

%e Array begins:

%e ==================================================================

%e n\k| 1 2 3 4 5 6 7 ...

%e ---|--------------------------------------------------------------

%e 1 | 1 2 3 4 5 6 7 ...

%e 2 | 2 8 18 32 50 72 98 ...

%e 3 | 3 24 81 192 375 648 1029 ...

%e 4 | 4 64 324 1024 2500 5184 9604 ...

%e 5 | 5 160 1215 5120 15625 38880 84035 ...

%e 6 | 6 384 4374 24576 93750 279936 705894 ...

%e 7 | 7 896 15309 114688 546875 1959552 5764801 ...

%e 8 | 8 2048 52488 524288 3125000 13436928 46118408 ...

%e 9 | 9 4608 177147 2359296 17578125 90699264 363182463 ...

%e ... - _Franck Maminirina Ramaharo_, Aug 07 2018

%t t[n_, k_] := Sum[k^n, {j, n}]; Table[ t[n - k + 1, k], {n, 10}, {k, n}] // Flatten (* _Robert G. Wilson v_, Aug 07 2018 *)

%Y Cf. a(n, 1) = a(1, k) = A000027(n); a(n, 2) = A036289(n); a(n, 3) = A036290(n); a(n, 4) = A018215(n); a(n, 5) = A036291(n); a(n, 6) = A036292(n); a(n, 7) = A036293(n); a(n, 8) = A036294(n); a(2, k) = A001105(k); a(3, k) = A117642(k); a(n, n) = A007778(n); a(n, n+1) = A066274(n+1): sum[a(i-1, n-i+1), {i, 1, n}] = A062807(n).

%K nonn,tabl

%O 1,2

%A _Ross La Haye_, Jan 22 2008

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)