19170

Appears in sequences

• a(n) = Sum_{i=1..floor((n+1)/4)} a(2*i-1) * a(n-2*i+1), with a(1)=3, a(2)=1, and a(3)=2.at n=10A024743
• Number of perifusenes with one internal vertex.at n=11A038382
• Numbers k such that k+1 is composite and divides 3^k-2^k.at n=33A068410
• a(n) = (-1)^n + (-2)^n - (-3)^n.at n=9A083321
• a(1)=1, a(2)=2; for n >= 2, a(n+1) = a(n) + sum of prime factors of a(n).at n=39A096461
• Numbers n for which there are exactly six k such that n = k + (product of nonzero digits of k).at n=11A096927
• a(n) is the smallest number k larger than a(n-1) such that n*d(k)*sopf(k)=sigma(k), where d is the number of divisors (A000005) and sopf the sum of prime factors without repetition (A008472).at n=19A134382
• Numbers n that raised to the powers from 1 to k (with k>=1) are multiple of the sum of their digits (n raised to k+1 must not be a multiple). Case k=8.at n=32A135193
• a(n) = (-1)^n + (-2)^n + 3^n (-1, -2 and 3 are the roots of the equation x^3 = 7*x + 6).at n=9A135399
• Expansion of g.f. (3-4*x-sqrt(1-4*x^2))/(2*(1-2*x)^2).at n=12A182555
• Number of 3-step one space leftwards or up, two space rightwards or down asymmetric rook's tours on an n X n board summed over all starting positions.at n=35A187298
• a(n+1) is the sum of a(n) and the prime factors of a(n), counted with multiplicity. Start with a(0) = 3.at n=23A192896
• Ordered differences of numbers 3^j-2^j, as in A001047.at n=28A205105
• s(k)-s(j), where (s(k),s(j)) is the least pair of numbers given by s(j)=3^j-2^j which n divides their difference.at n=26A205110
• Number T(n,k) of self-inverse permutations p on [n] where the minimal transposition distance equals k (k=0 for the identity permutation); triangle T(n,k), n>=0, 0<=k<=n, read by rows.at n=67A239145
• G.f. A(x) satisfies: coefficient of x^n in A(x)^(2*n) equals A000172(n) = Sum_{k=0..n} C(n,k)^3, the n-th Franel number.at n=11A242903
• Triangle read by rows: T(n,k) = number of neighbors in n-dimensional lattice for generalized neighborhood given with parameter k.at n=43A265014
• Numbers k such that 7*10^k - 23 is prime.at n=25A272271
• Square array T(n,k) = k^n - Sum_{0 < i < k} e(i)*(k-i)^n where e(i) = 1 if the partial sum up to this term would remain <= k^n, or 0 else; n, k >= 1; read by falling antidiagonals.at n=63A332099
• Numbers k such that k and k + 1 are both Niven numbers in base 3/2 (A342426).at n=35A342427