491536

Appears in sequences

• a(n) = n^4 - (n-1)^4 + (n-2)^4 - ... 0^4.at n=31A062392
• Doubly hexagonal numbers.at n=16A063249
• Triangular numbers such that the product of digits is also a (positive) triangular number.at n=33A069077
• Triangular numbers whose sum of aliquot divisors is also a triangular number.at n=13A083675
• Admirable triangular numbers.at n=4A109750
• Numbers k for which phi(k^2) = phi(k-1) * phi(k+1).at n=12A220169
• 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=31A225789
• Triangular numbers n such that sigma(n) is a square number.at n=26A256151
• Let x be the sum of the divisors d_i of k such that d_i | sigma(k). Sequence lists the numbers k for which x^2 = sigma(k).at n=15A284283
• Solutions to A000010(x) + A000010(x-1) = A000010(2*x).at n=30A299535
• Quadratically perfect numbers: numbers k such that (sigma(k) - 2k)^2 = sigma(k).at n=3A339599