21115

Appears in sequences

• Nearest integer to Gamma(n + 7/9)/Gamma(7/9).at n=8A020020
• Integer part of Gamma(n+7/9)/Gamma(7/9).at n=8A020065
• Number of planar cata-polyhexes with n cells.at n=10A038142
• Number of (2,n)-partitions of a chain of length n^3.at n=5A055659
• Nonprimes whose sum of digits is equal to its product of digits.at n=40A066307
• Triangular numbers with sum of digits = 10.at n=26A068129
• Triangular numbers which are a concatenation of two or more positive triangular numbers.at n=29A068144
• Triangular numbers such that the product of digits is also a (positive) triangular number.at n=14A069077
• Triangular number x such that x + reverse of x is a prime.at n=8A072387
• Triangular numbers which are also happy numbers (cf. A007770).at n=31A076712
• Expansion of 1/(1-x+2*x^2+2*x^3).at n=18A077956
• Expansion of 1/(1+x+2*x^2-2*x^3).at n=18A077977
• Diagonal of array A085205.at n=21A085228
• Triangle read by rows in which the n-th row contains the n smallest triangular numbers with the least significant digits of the n-th triangular number.at n=14A095225
• Diagonal of the triangle A095225.at n=4A095226
• Triangular numbers equal to the sum of a prime number with its index.at n=17A115886
• Hexagonal numbers with prime indices.at n=26A117961
• Numbers which are both lucky and triangular.at n=37A118565
• Triangular numbers composed of digits {1,2,5}.at n=8A119101
• Triangular numbers congruent to 1 or 5 mod 6.at n=34A128880