18315

Appears in sequences

• Numbers k such that phi(k) = phi(k+1).at n=20A001274
• Number of nonempty subsets of {1,2,...,n} in which exactly 2/3 of the elements are <= sqrt(n).at n=42A048095
• Number of degree-n even permutations of order exactly 2.at n=10A048099
• a(n) = floor( n^e ), e = 2.718281828...at n=36A061293
• Integers k such that k*28*c + 1 is prime for c = 1, 2, 4, 7 and 14.at n=8A067199
• Triangle read by rows: T(n,k) is the number of noncrossing connected graphs on n nodes on a circle, having exactly k four-sided faces, n>=2, 0<=k<=floor(n/2)-1.at n=18A094046
• A sequence derived from pentagonal numbers, or a Stirling number of the first kind matrix.at n=17A094952
• Number of different values assumed by a/b+c/d as a,b,c,d range between 1 and n.at n=19A119868
• A number n is included in the sequence if and only if the n-th integer from among those positive integers which are coprime to n+1 = the (n+1)-st integer from among those positive integers which are coprime to n.at n=8A139766
• a(n) = n*(n^2 + 3*n + 5)/3.at n=37A145069
• a(n) = number of elements of order n in simple group Alt(11) of order 19958400.at n=1A145822
• 9 times pentagonal numbers: 9*n*(3*n-1)/2.at n=37A152996
• Expansion of x^4*(2-6*x+5*x^2+2*x^3-4*x^4)/((1-x)^2*(1-2*x)^5).at n=10A219758
• Numbers k such that (6*k+1)*(12*k+1)*(18*k+1) is a Carmichael number which is the product of four prime numbers.at n=23A221743
• Limit of rows, when read in reverse, of triangle A227372.at n=22A227377
• Number of (2+1) X (n+1) 0..1 arrays with every 2 X 2 subblock ne-sw antidiagonal difference nondecreasing horizontally and nw+se diagonal sum nondecreasing vertically.at n=29A258555
• Magic sums of 4 X 4 magic squares composed of squares.at n=36A271580
• a(n) = 3*T(A285984(n)), where T(m) is the m-th triangular number A000217(m).at n=1A286035
• Irregular triangle read by rows: T(n,k) is the number of compositions of 2^n into k powers of 2.at n=39A323840
• Number of ways to write n as an ordered sum of nine powers of 2.at n=23A342252