28920

Appears in sequences

• Convolution of A000203 with itself.at n=38A000385
• Numbers k such that the least term in the periodic part of the continued fraction for sqrt(k) is 17.at n=9A031695
• a(n) = (n^2-1)*(2*n^2-1).at n=11A033595
• Triangular numbers with sum of digits = 21.at n=20A068131
• Triangular numbers which are 6-almost primes.at n=21A076580
• a(n) = (9*n^2+3*n+1) * n!.at n=5A082036
• A square array of quadratic-factorial numbers, read by antidiagonals.at n=41A082038
• a(n) = p(n)*(p(n)-1)/2 where p(n) = upper member of n-th pair of twin primes.at n=16A082669
• Triangular numbers whose sum of squared digits is also triangular.at n=18A094890
• Smith triangular numbers.at n=9A098840
• a(n) = n*(n+1)*(n^2+n+1)/2.at n=15A110450
• Triangular numbers for which the sum of the digits is an octagonal number.at n=23A117523
• Numbers k for which 2*k-1, 4*k-1, 8*k-1 and 16*k-1 are primes.at n=25A124494
• a(n) = 289n^2 + 2n.at n=9A158254
• Smallest number m such that A174903(m) = n.at n=26A174904
• Triangular numbers k whose divisors can be partitioned into three disjoint sets whose sums are all sigma(k)/3.at n=17A206025
• Numbers which are both the sum of n+1 consecutive triangular numbers and the sum of the n-1 immediately following triangular numbers.at n=8A222716
• Number of partitions p of n containing round((min(p) + max(p))/2) as a part.at n=44A238486
• Triangular numbers A000217 composed of only curved digits {0, 2, 3, 5, 6, 8, 9}.at n=46A247016
• Triangular numbers that are the product of a triangular number and a prime number.at n=44A253651