20898

Appears in sequences

• Number of non-vanishing Feynman diagrams of order 2n for the vacuum polarization (the proper two-point function of the photon) and for the self-energy (the proper two-point function of the electron) in quantum electrodynamics (QED).at n=5A005412
• Euler transform of reduced totient function psi(n), cf. A002322.at n=22A061257
• 3 times 13-gonal (or tridecagonal) numbers: a(n) = 3*n*(11*n - 9)/2.at n=36A153875
• Sequence of the "Natural Jewels": a natural jewel is a number that is totally enclosed by prime numbers in a version of Ulam Spiral.at n=15A172294
• Number of partitions of n+9 with largest inscribed rectangle having area <= n.at n=28A218630
• A(n,k) is the sum over all Dyck paths of semilength n of products over all peaks p of (x_p+k*y_p)/y_p, where x_p and y_p are the coordinates of peak p; square array A(n,k), n>=0, k>=0, read by antidiagonals.at n=33A258219
• Expansion of Product_{k>=1} ((1 + x^(2*k-1))/(1 - x^(2*k-1)))^(k*(k-1)/2).at n=25A294779
• Triangle read by rows: T(n,0) = 0 for n >= 0; T(n,2*k+1) = A152842(2*n,2*(n-k)) and T(n,2*k) = A152842(2*n,2*(n-k)+1) for n >= k > 0.at n=45A299989
• Expansion of 1/(2 - Product_{k>=1} (1 + x^(2*k-1))).at n=19A307058
• Numbers on the square spiral board that are enclosed by four primes.at n=16A341542
• Members of A014574 with sum of prime factors (with multiplicity) also in A014574.at n=18A349455
• Expansion of 1/(1 - x/(1 - 4*x)^(1/2))^3.at n=7A382540