28203

Appears in sequences

• Triangular numbers with sum of digits = 15.at n=33A068130
• Triangular numbers with internal digits also forming a triangular number.at n=35A069702
• Triangular numbers obtained as a concatenation of successive terms of A081847.at n=18A082235
• Hexagonal numbers for which the sum of the digits is also a hexagonal number.at n=26A117062
• Hexagonal numbers for which both the sum of the digits and the product of the digits are also hexagonal numbers.at n=15A117064
• Indices n such that the 3 X 3 matrix with components (row by row) prime(n+k), 0 <= k <= 8, has zero determinant.at n=32A117345
• a(n) = 441*n^2 - 21.at n=7A145678
• a(n) = 64*n^2 - n.at n=20A157948
• Number of 2 X 2 matrices M with all terms in {1,...,n} and permanent(M) >= n.at n=13A212240
• a(n) = least triangular number t > 0 such that n*t is a triangular number, or 0 if no such t exists.at n=31A227054
• Triangular numbers A000217 composed of only curved digits {0, 2, 3, 5, 6, 8, 9}.at n=44A247016
• Number of 3 X n 0..1 arrays with every element equal to 0, 1, 3 or 5 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero.at n=13A302428
• Triangular numbers that are the product of four distinct primes.at n=35A333771
• a(n) is the number of paths in the Z X Z grid joining (0,0) and (n,n) each of whose steps increases the Euclidean distance to the origin and has coordinates with absolute value at most 1.at n=5A346539
• Number A(n,k) of k-dimensional lattice walks from {n}^k to {0}^k using steps that decrease the Euclidean distance to the origin and that change each coordinate by at most 1; square array A(n,k), n>=0, k>=0, read by antidiagonals.at n=33A347811
• a(n) = number of isogeny classes of abelian surfaces over the finite field of order prime(n).at n=42A362198
• Tetraprimes (or products of exactly four distinct prime numbers) that are the sum of two successive tetraprimes.at n=9A380348
• Hexagonal numbers that are products of exactly four distinct primes.at n=19A381920
• a(n) is zero if n is a square, otherwise a(n) is the least triangular number m > 0 such that m*n is a triangular number.at n=31A389657