67100672

Appears in sequences

• Number of h-cobordism classes of smooth homotopy n-spheres.at n=26A001676
• Expansion of g.f.: 2*x*(1-x)/((1-2*x)*(1-2*x^2)).at n=26A014236
• a(n) = 4^n - 2^n.at n=13A020522
• Number of reversible strings with n beads of 2 colors. If more than 1 bead, not palindromic.at n=26A032085
• Sum of every 4th entry of row n in Pascal's triangle, starting at "n choose 0".at n=28A038503
• Number of elements of GF(2^n) with trace 0 and subtrace 1.at n=28A038519
• Number of 2n-bead balanced binary necklaces which are equivalent to their reversed complement, but not equivalent to their reverse and complement.at n=27A045678
• Numbers k such that the sums of the odd and even aliquot parts of k both divide k.at n=5A065125
• Numbers k such that sigma(k) = 3k - 2*phi(k).at n=18A068414
• a(n) = Sum_{k=0..n} binomial(4*n,4*k).at n=7A070775
• Numbers k such that there is a proper divisor d of k satisfying sigma(d)=k.at n=11A081756
• Composite numbers j such that binomial(2*j,j) == 2^j (mod j).at n=14A084699
• Sum of odd entries in row n of Pascal's triangle.at n=28A088560
• Fixed points of 1+Phi power sigma function 1PhiPsigma: integers m such that 1PhiPsigma(m) = m, where for j = Product p_i^r_i, 1PhiPsigma(j) = Product_i Sum_{0 <= s_i <= r_i, s_i is 0 or coprime to r_i} p_i^s_i.at n=7A095724
• Admirable oblong numbers.at n=9A109547
• Number of compositions of n with an odd number of 1's.at n=27A113980
• G.f.: 1/((1-2*x)*(1-2*x^2)).at n=25A122746
• a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3), n > 3; a(0) = 1, a(1) = 4, a(2) = 12, a(3) = 32.at n=24A133212
• Twice even perfect numbers. Also a(n) = M(n)*(M(n)+1), where M(n) is the n-th Mersenne prime A000668(n).at n=4A139256
• Numbers k such that the maximal prime power divisors of k form a nontrivial run of integers.at n=11A141808