This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A277211 Number of n X n X n triangular 0..1 arrays with no 2 X 2 X 2 subblock having three equal elements. 0
 1, 2, 6, 24, 130, 960, 9702, 134512, 2562516, 67152240, 2422643366, 120395521752, 8245524190254, 778511553019200, 101361018574446630, 18202576574465956224, 4509516189662784365688, 1541444043912873505870464, 727078284287957812245097914 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS FORMULA a(n) = 2*A007017(n-1) for n>0. - Alois P. Heinz, Nov 05 2016 EXAMPLE Some solutions for n=3:      0      0      0      1      1      1     0 1    1 0    1 1    0 0    1 0    0 1    1 0 0  0 1 1  1 0 1  0 1 1  0 0 1  1 1 0 PROG (PARI) nextrowcomb(rowarr) = my(k=#rowarr, i=0); while(rowarr[k]==1, rowarr[k]=0; i++; k--); while(rowarr[k]==0 && k > 1, k--); if(rowarr[k]==1, rowarr[k]=0; rowarr[k+1]=1; k=k+2; while(i > 0, rowarr[k]=1; k++; i--), for(x=k, k+i, rowarr[x]=1)); rowarr is_validcombination(toprow, bottomrow) = for(v=1, #toprow, if(toprow[v]==bottomrow[v] && toprow[v]==bottomrow[v+1], return(0))); for(w=2, #toprow, if(toprow[w-1]==bottomrow[w] && toprow[w]==bottomrow[w], return(0))); return(1) terms(n) = my(toprows=[[0], [1]], bottomrow=[0, 0], validrows=[]); while(1, for(k=1, #toprows, if(is_validcombination(toprows[k], bottomrow), validrows=concat(validrows, [bottomrow]))); if(vecmin(bottomrow)==1, bottomrow=vector(#bottomrow+1); print1(#validrows, ", "); toprows=validrows; validrows=[], bottomrow=nextrowcomb(bottomrow)); if(#bottomrow==n+2, break)) terms(5) \\ print initial five terms CROSSREFS Cf. A007017, A271069, A271333, A271400. Sequence in context: A201158 A191343 A052862 * A216779 A129101 A292907 Adjacent sequences:  A277208 A277209 A277210 * A277212 A277213 A277214 KEYWORD nonn AUTHOR Felix FrÃ¶hlich, Nov 05 2016 EXTENSIONS Thanks to R. H. Hardin and Charles R Greathouse IV for helpful suggestions. a(7)-a(18) from Alois P. Heinz, Nov 05 2016 STATUS approved

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

Last modified October 23 20:19 EDT 2018. Contains 316530 sequences. (Running on oeis4.)