18230

Appears in sequences

• Let c(k) denote the k-th composite number and p(k) the k-th prime number; then a(n) = Sum_{i=n*(n-1)/2+1 .. n*(n+1)/2} c(i) - Sum_{i=1..n} p(i).at n=31A024850
• Numbers k such that the least term in the periodic part of the continued fraction for sqrt(k) is 54.at n=4A031732
• Let u(0)=1, u(n) = 5/2 * floor(u(n-1)); then a(n) = (2/5)*u(n).at n=11A076883
• Expansion of 1 + Sum_{i>=1} (x^prime(i)/Product_{j=1..i} (1-x^j)).at n=52A095700
• Expansion of 1/(sqrt(1-2x-3x^2)-x).at n=9A111961
• a(n) = 25*n^2 + 5.at n=26A158445
• Monotonic ordering of set S generated by these rules: if x and y are in S then floor(x*y/2) is in S, and 5 is in S.at n=40A192520
• Numbers k such that (82*10^k + 161)/9 is prime.at n=28A271505
• Number of sets of exactly n positive integers <= n+5 having a square element sum.at n=39A281968
• a(n) = a(n-1) - a(n-2) + 3*a(n-3) with a(0) = 1, a(1) = 2 and a(2) = 4.at n=21A356849
• Number of integer partitions of n where the parts do not have the same median as the distinct parts.at n=37A360244
• Antichain-Chain Quilt Numbers: Square table of the number of ASM quilts of type A_2(j) x C_k read down antidiagonals, where C_k is the chain poset or rank k and A_2(j) is the rank 2 poset with a unique minimal and maximal element and j atoms.at n=50A374822