19145

Appears in sequences

• a(n) = floor( n*(n-1)*(n-2)*(n-3)/22 ).at n=27A011932
• Hard numbers: a(n) = smallest positive number m with f(m) = n, where f(m) is the smallest number of digits that are needed to construct m using only 1's, 2's and any number of +, -, *, ^ signs, allowing concatenation of the digits.at n=10A060273
• Number of permutations satisfying -k<=p(i)-i<=r and p(i)-i not in I, i=1..n, with k=3, r=3, I={-1,2}.at n=14A079990
• Sum of first n 6-almost primes.at n=34A086052
• Consider the family of multigraphs enriched by the species of partitions. Sequence gives the triangle read by rows giving coefficients of polynomials arising from enumeration of those multigraphs on n edges.at n=30A098315
• G.f.: 1/((1-t^10)*(1-t)*(1-t^3)*(1-t^5)*(1-t^7)*(1-t^9)*(1-t^11)*(1-t^13)*(1-t^15)*(1-t^17)*(1-t^19)).at n=66A266750
• Numbers k such that N = k^6 is a twin rank (cf. A002822: 6N +- 1 are twin primes).at n=11A326236