195000

Appears in sequences

• Number of reversible strings with n beads of 5 colors. If more than 1 bead, not palindromic.at n=7A032088
• Triangular numbers which are 9-almost primes.at n=2A076583
• Smallest triangular number having n^2 as divisor.at n=24A080983
• a(n) = n^2 * (n^2 - 1)/2.at n=24A083374
• Expansion of g.f. 1/((1-x^2+x^3+x^4-x^5)*(1-x-x^2+x^3-x^5)).at n=34A147598
• G.f.: A(x) = F(x*G(x)^4) = F(G(x)-1) where F(x) = G(x/F(x)^2) = 1 + x*F(x)^2 is the g.f. of A000108 (Catalan) and G(x) = F(x*G(x)^2) = 1 + x*G(x)^4 is the g.f. of A002293.at n=7A153397
• a(n) = 5^n*(5^n-1)/2.at n=4A162729
• Triangular numbers that are sums of twin prime pairs.at n=22A165966
• Let T(n) = n(n+1)/2 be the n-th triangular number (A000217); a(n) = T(8T(n)).at n=12A185096
• Number of 2 X 2 matrices with all terms in {0,1,...,n} and odd trace.at n=24A210379
• Smallest triangular number divisible by 10^n.at n=2A228188
• Total sum of cubed lengths of ascending runs in all permutations of [n].at n=7A229003
• Triangular numbers that are the product of a triangular number and a square number (both greater than 1).at n=11A253650
• Triangular numbers that are the product of a triangular number and an oblong number.at n=31A253652
• Numbers that are product of a second hexagonal number (A014105) and a square pyramidal numbers (A000330) in at least two ways.at n=21A306122
• First quadrisection of A332843.at n=27A330522