17951

Appears in sequences

• Composite numbers whose divisors (except 1) all contain the digit 9.at n=31A062680
• Expansion of (1-x)/(1+2*x-x^2+2*x^3).at n=10A078059
• Numbers k such that sigma(k) - phi(k) is a 4th power.at n=21A115918
• a(0)=1, a(1)=1, a(n) = 11*a(n/2) for even n, and a(n) = 10*a((n-1)/2) + a((n+1)/2) for odd n >= 3.at n=23A116525
• a(n) = n*(n^2 - 1)/2 - 1.at n=31A117560
• The Wiener index of a chain of n triangles (i.e., joined like VVV..VV; here V is a triangle!).at n=28A143941
• Numbers n such that the sum of the squares of the digits of n^n is a square.at n=20A171976
• A positive integer n is included if n, when written in binary, is made of run-lengths (lengths of runs of 0's as well as of runs of 1's) that form a permutation of some number of consecutive positive integers starting with 1.at n=46A175061
• Numbers that can be written in more than 1 way as p^2 + 3pq + q^2 with primes p < q.at n=10A218795
• Numbers n with nonzero digits such that n*(product of digits of n) is a palindrome.at n=35A229550
• Indices of the start of 10 successive distinct digits in the decimal expansion of e (2.718281828...).at n=13A258166
• Number of primes p of the form k^2 + 1 less than 10^n such that p+2 and 2p+1 are also primes.at n=16A356364
• a(n) is the first position where the digits of n occur simultaneously in the decimal expansions of Pi and e.at n=16A381980