72010

Appears in sequences

• Molien series of 4-dimensional representation of u.g.g.r. #9.at n=27A013977
• Numbers k such that k | 10^k + 10.at n=26A015902
• Number of singular 2 X 2 matrices over Z(n) (i.e., with determinant = 0).at n=37A020478
• Even triangular numbers with prime indices.at n=38A034955
• Numbers n such that n | 4^n + 3^n + 2^n + 1^n.at n=35A056643
• a(n) = n^4 - (n-1)^4 + (n-2)^4 - ... 0^4.at n=19A062392
• Doubly hexagonal numbers.at n=10A063249
• Triangular numbers with sum of digits = 10.at n=34A068129
• Triangular number x such that x + reverse of x is a prime.at n=20A072387
• Smallest triangular number greater than n! with the same leading digits as n!.at n=5A096564
• Triangular numbers whose digit reversal is a brilliant number (A078972).at n=10A115678
• a(n) = n*(8*n^2 + 1)/3.at n=30A143166
• Triangular numbers p*(p+1)/2 with p prime such that 1+(number of prime factors of p+1) is prime.at n=31A144549
• Number of n X 4 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 0 1 and 1 0 1 vertically.at n=18A207449
• Triangular numbers T from A000217 such that (4*T+1)/13 is prime.at n=22A208294
• Least triangular number of the form p*triangular(n) where p is a prime number, or 0 if no such triangular number exists.at n=19A225789
• a(n) = A000217(A000217(n)+1).at n=27A267707
• Number of inequivalent (modulo C_4 rotations) square n X n grids with squares coming in two colors and three squares have one of the colors.at n=9A275799
• a(n) = Sum_{1 <= x_1, x_2 <= n} sigma( n/gcd(x_1, x_2, n) ).at n=37A373129
• Hexagonal numbers that are products of exactly four distinct primes.at n=32A381920