57121

Appears in sequences

• a(n)-th triangular number is a square: a(n+1) = 6*a(n) - a(n-1) + 2, with a(0) = 0, a(1) = 1.at n=7A001108
• Squares of NSW numbers (A002315): x^2 such that x^2 - 2y^2 = -1 for some y.at n=3A008843
• a(n) = (8*n + 7)^2.at n=29A017150
• a(n) = (9*n + 5)^2.at n=26A017222
• a(n) = (10*n + 9)^2.at n=23A017378
• a(n) = (11*n + 8)^2.at n=21A017486
• a(n) = (12*n + 11)^2.at n=19A017654
• Squares which are palindromes in base 14.at n=12A030074
• Square numbers that are concatenations of two or more prime numbers.at n=38A038692
• Squares with initial digit '5'.at n=24A045788
• Squares resulting from procedure described in A048383.at n=11A048384
• Expansion of 1/((1 - x)*(1 - 2*x - x^2)).at n=12A048739
• Numbers that are not squarefree and whose Euler totient function is squarefree.at n=40A049198
• Prime powers p^w (w >= 2) such that p^w-2 is prime.at n=33A053704
• Numbers k such that k^12 == 1 (mod 13^4).at n=23A056095
• a(n) = n*(n+1)*(n+2)*(n+3)+1 = (n^2 + 3*n + 1)^2.at n=14A062938
• Numbers k such that sigma(k)*phi(k) is squarefree.at n=24A065299
• Composite numbers k such that the sum of the divisors of k^2 is a prime.at n=26A065405
• Numbers k such that sigma_4(k)/sigma_2(k) is prime.at n=15A066109
• Number of 13 X n binary arrays with path of adjacent 1's from upper right corner to lower left corner.at n=1A069335