21312

Appears in sequences

• Number of ways of writing n as a sum of 8 squares.at n=11A000143
• Theta series of E_8 lattice with respect to deep hole.at n=10A004017
• Theta series of {D_8}* lattice.at n=11A008427
• a(n) = (2*n - 11)*n^2.at n=24A015245
• Palindromes of form k*(k+4).at n=7A028556
• Theta series of 8-d 6-modular lattice G_2 tensor F_4 (or A_2 tensor D_4) with det 1296 and minimal norm 4 in powers of q^2.at n=14A028977
• Cubeful (i.e., not cubefree) palindromes.at n=33A035133
• Base-10 palindromes that start with 2.at n=35A043037
• Palindromes that are divisible by 6.at n=33A045641
• Palindromic and divisible by 8.at n=24A045643
• Palindromic and divisible by 9.at n=35A045644
• Largest palindromic substring in 2^n.at n=49A046260
• Palindromes with exactly 9 prime factors (counted with multiplicity).at n=2A046335
• Composite palindromes whose sum of prime factors is palindromic (counted with multiplicity).at n=33A046354
• Sum of digits of zero-absent composite a(n) equals number of prime factors.at n=6A050690
• a(n)=phi(n^2+1)/n if (n^2+1) is composite and phi(n^2+1)==0 (mod n).at n=33A067926
• Numbers divisible by the sum of factorials of their digits [A061602(n)] and also terminate in the sum of factorials of their digits.at n=16A071064
• Palindromes arising in A083125. a(n) = A083125(n)*A083125(n+1).at n=41A083126
• a(1) = 3, a(n) = smallest nontrivial palindromic multiple of a(n-1). a(n) is not equal to a(n-1) or a concatenation of a(n-1) with itself.at n=5A083149
• a(1) = 1; for n > 1, a(n) is the smallest number that is either a divisor or a multiple, in that priority (order), of a(n-1) such that it is a distinct palindrome not included earlier.at n=44A089337