19191

Appears in sequences

• Palindromes of form k^2 + k + 9.at n=8A027727
• 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 92.at n=34A031590
• Largest palindromic substring in 6^n.at n=44A046264
• Numbers whose consecutive digits differ by 8.at n=19A048410
• Palindromes with more than 3 digits in which the absolute difference of a pair of successive digits is identical.at n=22A085109
• a(1) = 2; then smallest palindrome > 1 not occurring earlier such that every partial concatenation is a prime.at n=38A088086
• Palindromes n such that 10n01 is a prime.at n=32A099744
• Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 0), (-1, 0, 1), (0, 0, -1), (1, -1, 0), (1, 1, 1)}.at n=8A149671
• Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 1), (0, 1, -1), (1, 0, 0), (1, 1, 0)}.at n=9A149876
• a(n) is the least number not occurring earlier such that neighboring digits sum to 1 or 10.at n=22A182396
• Numbers n such that the n-th digit (after the decimal point) in the decimal expansion of Pi are the occurrence of the least significant digit represented by the more significant digits.at n=16A201545
• Semiprimes formed by concatenating n, n, and 1 for n = 1, 2, 3,....at n=8A210711
• Integers of the form 8k + 7 that can be written as a sum of four distinct squares of the form m, m + 2, m + 3, m + 4, where m == 2 (mod 4).at n=16A243581
• Consider a decimal number of k>=2 digits x = d_(k)*10^(k-1) + d_(k-1)*10^(k-2) + … + d_(2)*10 + d_(1) and the transform T(x)-> (d_(k)+d_(k-1) mod 10)*10^(k-1) + (d_(k-1)+d_(k-2) mod 10)*10^(k-2) + … + (d_(2)+d_(1) mod 10)*10 + (d_(1)+d(k) mod 10). Sequence lists the numbers x such that T(x)=0.at n=27A243994
• Numbers k with the property that the square root of the product of the digits of k is equal to the sum of the square roots of its digits.at n=28A281745
• Numbers using only digits 1 and 9.at n=40A284294
• G.f. A(x) satisfies: 1 = Sum_{n>=0} x^n / (1-x)^( n*(n+1)/2 ) / A(x)^( (n+1)*(n+2)/2 ).at n=20A296230
• Number of nX6 0..1 arrays with every element equal to 0, 1, 2 or 3 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero.at n=2A302263
• T(n,k)=Number of nXk 0..1 arrays with every element equal to 0, 1, 2 or 3 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero.at n=30A302265
• Number of 3 X n 0..1 arrays with every element equal to 0, 1, 2 or 3 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero.at n=5A302267