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

Author

Vladimir Shevelev, Apr 12 2010

Keywords

• nonn

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

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

Crossrefs

Cf. A176211, A176210, A000211.

Programs

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