191919

Appears in sequences

• Number of exterior points formed by extending diagonals of n-gon in general position.at n=36A005701
• Denominator of (2n+1)(2n+2) B_{2n}, where B_n are the Bernoulli numbers. Also denominators of the asymptotic expansion of the polygamma function psi'''(z).at n=55A006956
• Numbers whose consecutive digits differ by 8.at n=22A048410
• Number of scalars which can be constructed from the Riemann tensor and metric tensor in n dimensions.at n=38A050297
• Numbers k such that phi(k)/lambda(k) increases to a record value, where phi(k) is the Euler totient function (A000010) and lambda(k) is the Carmichael lambda function (A002322).at n=28A066605
• a(n) = lcm(n, n+1, n+2, n+3, n+4) / 60.at n=34A067048
• Triplets: base 10 representation is the juxtaposition of three identical strings.at n=18A074842
• a(n) = n*(n-1)*(n-2)*(n+3)/12.at n=39A117662
• The 3rd Witt transform of A000027.at n=37A147611
• A121153 \ A005836.at n=24A170830
• a(n) is the least number not occurring earlier such that neighboring digits sum to 1 or 10.at n=31A182396
• List of words over {1,9} with equal numbers of 1's and 9's.at n=13A214532
• 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=36A243994
• 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 x divides T(x).at n=39A244287
• Squarefree integers m > 1 such that if prime p divides m, then s_p(m) >= p and s_p(m) == 3 (mod p-1), where s_p(m) is the sum of the base p digits of m.at n=23A324405
• Numbers k such that the infinite sequence of digits consisting of the final digit of k^m for m = 2, 3, 4, ... is the same as the sequence of digits obtained by concatenating infinitely many copies of k.at n=25A344555
• Numbers m with decimal expansion (d_k, ..., d_1) such that d_i = m ^ i mod 10 for i = 1..k.at n=47A344749
• Numbers k such that k and k+1 both have at least three divisors with the same value of the Euler totient function (A000010).at n=4A373529