18207

Appears in sequences

• Number of walks on square lattice.at n=13A005565
• a(n) = floor(a(n-1)*3/2) with a(1) = 2.at n=23A061418
• Number of numbers whose base-3/2 expansion (see A024629) has n digits.at n=23A081848
• Triangle read by rows: T(n,k), n >=1, 0 <= k <= C(n,k), = number of n X n symmetric positive semi-definite matrices with 2's on the main diagonal and 1's and 0's elsewhere and with k 1's above the diagonal.at n=46A083029
• a(1) = 1; for n > 1: if n is even, a(n) = least k > 0 such that sum(i=1,n/2,a(2*i-1))/sum(j=1,n,a(j))>=1/4, or 1 if there is no such k; if n is odd, a(n) = largest k > 0 such that sum(i=1,(n+1)/2,a(2*i-1))/sum(j=1,n,a(j))<=1/3, or 1 if there is no such k.at n=49A104740
• Sum of the first n n-digit primes less n*10^(n-1).at n=24A114053
• 3 times 9-gonal (or nonagonal) numbers: a(n) = 3*n*(7*n-5)/2.at n=42A152759
• Triangle T(n, k) = T(n-1, k) + T(n-1, k-1) + ((n+1)^2*(n+2)^2*(2*n^2 +6*n +3)/12)*T(n-2, k-1), read by rows.at n=16A154231
• Triangle T(n, k) = T(n-1, k) + T(n-1, k-1) + ((n+1)^2*(n+2)^2*(2*n^2 +6*n +3)/12)*T(n-2, k-1), read by rows.at n=19A154231
• Number of nondecreasing integer sequences of length 24 with sum zero and sum of absolute values 2n.at n=13A158158
• a(n) = 225*n^2 - 2*n.at n=8A158226
• Number of subsets of {1,2,...,n-10} without differences equal to 2, 4, 6, 8 or 10.at n=45A224812
• Amicable totient numbers: pairs of numbers (m, n) such that n = A092693(m) and m = A092693(n).at n=3A286233
• Numbers m such that 20*m + 1, 80*m + 1, 100*m + 1, and 200*m + 1 are all primes.at n=24A372186