20728

Appears in sequences

• Numbers k such that phi((prime(k)-1)/2) = sigma(k).at n=43A068474
• Poincaré series [or Poincare series] P(C#_{3,2}; x).at n=29A124630
• Expansion of 1/(1 - x^4 - x^5 - x^6 + x^10).at n=58A147652
• a(n) = 64*n^2 - 8.at n=17A158487
• Number of permutations of 1..n with displacements restricted to {-6,-5,-4,-3,-1,0,2}.at n=14A189594
• Number of tilings of a 7 X n rectangle using integer-sided square tiles of area > 1.at n=39A226371
• Number of length 3 1..(n+2) arrays with no leading or trailing partial sum equal to a prime.at n=42A254206
• Expansion of Sum_{i>=1} mu(i)^2*x^i/(1 - x^i) * Product_{j=1..i} 1/(1 - mu(j)^2*x^j), where mu() is the Moebius function (A008683).at n=43A284835
• a(n) is the number of regions formed by n-secting the angles of an octagon.at n=39A335769
• E.g.f. satisfies A(x) = exp(x * (1 + x + x^2 + x^3) * A(x^4/24)).at n=7A367756
• Expansion of 1 / ((1-x)^2 - x^4)^2.at n=15A392552