21912

Appears in sequences

• Numbers k such that the least term in the periodic part of the continued fraction for sqrt(k) is 37.at n=3A031715
• Cubeful (i.e., not cubefree) palindromes.at n=36A035133
• Base-10 palindromes that start with 2.at n=41A043037
• Numbers that are palindromic, divisible by 11 and have an odd number of digits.at n=18A045571
• Palindromes that are divisible by 6.at n=35A045641
• Palindromic and divisible by 8.at n=27A045643
• Palindromes with exactly 6 prime factors (counted with multiplicity).at n=6A046332
• Palindromes expressible as the sum of 2 consecutive palindromic primes.at n=6A046490
• a(n) = smallest palindrome > a(n-1) such that a(1)*a(2)*...*a(n) - 1 is a prime.at n=28A051954
• a(n) is the odd-length palindrome whose digits up to the center are those of n and whose center digit is equal to the digital root of the product of the factorial of n and the reverse of n.at n=20A082941
• Smallest palindromic multiple of 11, sum of whose digits at some stage is equal to n.at n=14A083516
• Numbers that can be expressed as the difference of the squares of primes in exactly five distinct ways.at n=24A092001
• Period length of continued fraction for square root of n-th decimal repunit.at n=9A096485
• a(1) = 1+2-3 = 0, a(2) = 4+5+6-7 = 8, a(3) = 8+9+10+11-12 = 26, a(4) = 13+14+15+16+17-18 = 57, ...at n=33A111694
• McKay-Thompson series of class 28B for the Monster group.at n=35A112169
• Number of walks within N^2 (the first quadrant of Z^2) starting at (0,0), ending on the vertical axis and consisting of n steps taken from {(-1, -1), (-1, 0), (-1, 1), (0, -1), (0, 1), (1, 0), (1, 1)}.at n=7A151491
• Triangle of coefficients of polynomials u(n,x) jointly generated with A208762; see the Formula section.at n=50A208761
• Numbers n such that n^16+1 and (n+2)^16+1 are both prime.at n=30A217991
• Number of n X 6 0..1 arrays with rows, diagonals and antidiagonals unimodal and columns nondecreasing.at n=7A223836
• Number of ballot sequences of length n with exactly 6 fixed points.at n=15A239117