19040

Appears in sequences

• Number of n-step walks on square lattice in the first quadrant which finish at distance n-3 from the x-axis.at n=31A005564
• E.g.f.: sec(tanh(x)*log(x+1))=1+12/4!*x^4-60/5!*x^5+90/6!*x^6-420/7!*x^7...at n=8A012657
• a(n) = Sum_{m=1..n} Sum_{k=1..m} prime(k).at n=31A014148
• Even octagonal numbers: a(n) = 4*n*(3*n-1).at n=40A014642
• a(n) in base 13 is a repdigit.at n=44A048337
• Triangle T(n,m) of number of labeled n-node T_0-hypergraphs with m distinct hyperedges (empty hyperedge excluded), m=0,1,...,2^n-1.at n=35A059087
• Number of functions f:{0,1,2,...,n} -> {0,1,2,...,n} that satisfy f(0)=0 and f(n)=0, with f nowhere concave upward.at n=13A068602
• Octagonal numbers for which the product of the digits is also an octagonal number.at n=34A117083
• Numbers n such that n^24 + 1 = p*q with p,q distinct primes.at n=32A119982
• Triangle T(n,k) = number of forests of labeled rooted trees of height at most 1, with n labels, k of which are used for root nodes and any root may contain >= 1 labels, n >= 0, 0<=k<=n.at n=39A143396
• a(n) = n*(n+1)*(n+2)*(n+3)/3.at n=14A162668
• Number of 2n-digit primes that are concatenation of n two-digit distinct primes p_1...p_n: 10<p_1<p_2<...<p_n>98.at n=10A168519
• The first n-fold intrinsically 4-palindromic number (represented in base ten).at n=2A171703
• The first 3-fold intrinsically n-palindromic number (given in base ten).at n=2A171741
• Numbers such that each digit from 0 to 9 appears at least 7 times in the digits of their divisors.at n=21A175507
• a(n) = number of 8-digit primes with digit sum n, where n runs through the non-multiples of 3 in the range [2..71].at n=10A178879
• Numbers of the form p^5*q*r*s where p, q, r, and s are distinct primes.at n=19A179704
• Numbers that are 4-digit palindromes in at least 2 bases.at n=24A180453
• Number of (n+1)X3 binary arrays with every 2X2 subblock determinant equal to exactly one or two horizontal and vertical neighbor 2X2 subblock determinants.at n=7A186895
• Number of (n+1)X9 binary arrays with every 2X2 subblock determinant equal to exactly one or two horizontal and vertical neighbor 2X2 subblock determinants.at n=1A186901