21612

Appears in sequences

• Even palindromes in which parity of digits alternates.at n=28A030149
• Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 98.at n=27A031596
• Numbers k such that the least term in the periodic part of the continued fraction for sqrt(k) is 98.at n=2A031776
• Base-10 palindromes that start with 2.at n=38A043037
• Palindromes that are divisible by 6.at n=34A045641
• McKay-Thompson series of class 34a for the Monster group.at n=43A058639
• a(n) = concatenate(n, A010888(2*n), reverse(n)), where A010888 = digital root.at n=20A082944
• Next-to-central column of triangle in A059317.at n=11A106053
• Palindromes sandwiched between twin primes.at n=7A113838
• Palindromic numbers that contain the sum of their digits as a substring.at n=22A121939
• Number of base 32 n-digit numbers with adjacent digits differing by one or less.at n=7A126386
• Right hand side of Pascal rhombus A059317.at n=56A160905
• Number of n X 7 binary arrays without the pattern 0 1 diagonally, vertically or antidiagonally.at n=30A188864
• The number of 3-length segments in all possible covers of L-length line by these segments with allowed gaps < 3.at n=30A228494
• Palindromic numbers such that the sum of the digits equals the number of divisors.at n=17A263720
• Irregular triangular array, read by rows: row n shows the coefficients of the polynomial p(n,x) defined in Comments.at n=11A329433
• a(n) = a(n-1)^2 + 3 for n >=2 , where a(0) = 1, a(1) = 3.at n=4A329471
• Number of partitions of the (n+4)-multiset {0,...,0,1,2,3,4} with n 0's into distinct multisets.at n=14A346824
• Palindromes that can be written as the sum of two palindromic primes.at n=34A356824