18239

Appears in sequences

• a(n) = n*(3*n^2 - 1)/2.at n=23A004188
• Number of subsets of { 1, ..., n } containing an A.P. of length 9.at n=20A018794
• Numbers k such that phi(k) + phi(k+1) divides sigma(k) + sigma(k+1).at n=24A067282
• a(1) = 1, a(2) = 2; for n >= 2, a(n+1) = a(n) + sum of the unique prime factors of a(n).at n=21A096460
• a(1)=1, a(2)=2; for n >= 2, a(n+1) = a(n) + sum of prime factors of a(n).at n=35A096461
• Numerators in binomial transform of 1/(n+1)^2.at n=6A097344
• Numerators of the partial sums of the binomial transform of 1/(n+1).at n=6A097345
• 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=19A192896
• Truncated octahedron with faces of centered polygons.at n=11A193228
• (p^2 - 3)/2 for odd primes p.at n=41A243887
• Numbers k with the property that it is possible to write the base 2 expansion of k as concat(a_2,b_2), with a_2>0 and b_2>0 such that, converting a_2 and b_2 to base 10 as a and b, we have sigma(a) + sigma (b) = sigma(k) - k.at n=28A258813
• Triangle T(n, k) read by rows: row n gives the coefficients of the row polynomials of the (n+1)-th diagonal sequence of the Sheffer triangle A094816 (special Poisson-Charlier).at n=42A290311
• Euler elliptic Carmichael numbers for the elliptic curve y^2 = x^3 + 80.at n=11A290338
• Elliptic Carmichael numbers for the elliptic curve y^2 = x^3 + 80.at n=21A317174
• a(n) is the smallest denominator D of the fraction N/D with 1 <= D < 2^n which is closest to (3/2)^n.at n=15A324204
• Indices k such that A358128(k) is a square.at n=45A358130
• a(n) is the number of integer triples (x,y,z) satisfying a system of linear inequalities and congruences specified in the comments.at n=33A370349
• Numbers of not uniquely embeddable trees on n vertices.at n=15A378673