26520

Appears in sequences

• Theta series of D_6 lattice.at n=20A008428
• Theta series of direct sum of 2 copies of f.c.c. lattice.at n=26A008663
• Aliquot sequence starting at 1074.at n=7A014364
• Numbers k such that 2047*2^k+1 is prime.at n=15A037177
• Convolution of Catalan numbers A000108 with Catalan numbers but C(0)=1 replaced by 3.at n=9A038629
• First element r of (-1)sigma sociable triple (r,s,t): s=(-1)sigma(r), t=(-1)sigma(s), r=(-1)sigma(t), where if x=Product p(i)^r(i), then (-1)sigma(x)=Product(-1+(Sum p(i)^s(i), s(i)=1 to r(i))).at n=23A049057
• a(n) = n*(2*n^2 - 2*n + 1).at n=24A059722
• Areas of Pythagorean triangles (A069482, A069484, A069486).at n=5A069487
• Triangle T(n,k) read by rows, given by [0, 1, 0, 1, 0, 1, 0, 1, 0, 1, ...] DELTA [1, 0, 2, 0, 3, 0, 4, 0, 5, 0, 6, 0, 7, ...] where DELTA is the operator defined in A084938.at n=63A086329
• Triangle read by rows of the numbers T(n,k) (n > 1, 0 < k < n) of set partitions of n of length k which do not have a proper subset of parts with a union equal to a subset {1,2,...,j} with j < n.at n=47A087903
• Numbers that can be expressed as the difference of the squares of primes in exactly seven distinct ways.at n=6A092003
• Numbers whose set of base 13 digits is {0,C}, where C base 13 = 12 base 10.at n=10A097259
• When the n-th term of this sequence is added to or subtracted from the square of the n-th prime of the form 4k + 1 (i.e., A002144(n)), the result in both cases is a square.at n=21A114200
• Terms of A061047 ending in 0.at n=31A146950
• a(n) = ((5 + sqrt(3))^n - (5 - sqrt(3))^n)/(2*sqrt(3)).at n=5A153596
• Numbers with exactly 64 divisors.at n=28A172443
• a(n) = 17*n*(n+1).at n=39A173308
• a(n) = sigma(2^(n-1)*a(n-1)) for n>1 with a(1)=1.at n=4A180710
• Numbers with prime factorization pqrst^3.at n=13A189984
• Common differences in triples of squares in arithmetic progression, that are not a multiples of other triples in (A198384, A198385, A198386).at n=34A198438