A176212 Terms of A176211, duplicates removed.

6, 9, 13, 20, 31, 36, 49, 54, 78, 81, 117, 120, 125, 169, 180, 186, 201, 216, 260, 279, 294, 324, 400, 403, 441, 468, 486, 523, 620, 637, 702, 720, 729, 750, 845, 961, 980, 1014, 1053, 1080, 1116, 1125, 1206, 1296, 1366, 1519, 1521, 1560, 1620, 1625, 1674, 1764, 1809, 1944, 2197

Offset

1,1

Comments

The terms are permanents of a set of certain symmetric (0,1)-matrices as detailed in A176211. Thus the sequence solves a symmetric version of Gristein problem: to find all the values of permanent of all square (0,1) matrices, which contain exactly three 1's in each row and column (see the list of unsolved problems in chapter 8 of Minc's book).

References

H. Minc, Permanents, Addison-Wesley, 1978.

Links

Table of n, a(n) for n=1..55.

V. S. Shevelev, Some problems of the theory of enumerating the permutations with restricted position, Journal of Soviet Mathematics, 61 (4) (1992) 2272-2317

Prog

(PARI) f(n) = fibonacci(n+1) + fibonacci(n-1) + 2; \\ A000211
lista(nn) = {my(v = vector(nn, k, f(k+2))); my(vmax = vecmax(v)); my(w =  vector(nn, k, [0, logint(vmax, v[k])])); my(list=List()); forvec(x = w, if (vecmax(x), my(y = prod(k=1, #v, v[k]^x[k])); if (y <= vmax, listput(list, y)); ); ); Vec(vecsort(list, , 8)); }
lista(14) \\ Michel Marcus, Jan 06 2021

Crossrefs

Cf. A176211, A176210, A000211.

Sequence in context: A315973 A315974 A176211 * A232553 A155705 A267369

Adjacent sequences: A176209 A176210 A176211 * A176213 A176214 A176215

Keyword

nonn

Author

Vladimir Shevelev, Apr 12 2010

Status

approved