[seqfan] Re: Trivial array of powers

Richard J. Mathar mathar at mpia-hd.mpg.de
Wed Dec 9 18:05:51 CET 2015


In http://list.seqfan.eu/pipermail/seqfan/2015-December/015806.html I 
was using "alphabet" in the usual sense of combinatorics.  Of course,
rejecting only words that have clusters of three or more repeated letters
is no longer a "trivial" array, but more like this:

     1      2      3      4      5      6      7      8 
     1      4      9     16     25     36     49     64 
     0      6     24     60    120    210    336    504 
     0     10     66    228    580   1230   2310   3976 
     0     16    180    864   2800   7200  15876  31360 
     0     26    492   3276  13520  42150 109116 247352 
     0     42   1344  12420  65280 246750 749952 1950984 
     0     68   3672  47088 315200 1444500 5154408 15388352 

with 2nd column in A006355, 3rd in A121907, 4th in A123620, 5th in A123871 etc.

Richard Mathar


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