27404

Appears in sequences

• Number of immersions of an unoriented circle into the oriented sphere with n double points.at n=8A008987
• Expansion of (3 + x^2) / (1 - x)^4.at n=33A037237
• a(n) = binomial(n+5,4) - 1.at n=25A063258
• Numbers k such that k and k+1 have the same sum of unitary divisors (A034448).at n=33A064125
• Numbers k such that sigma(k+1) = 5*phi(k).at n=8A067263
• Numbers k such that both k and k+1 are abundant.at n=7A096399
• Numbers k such that both sigma(k) >= 2*k-1 and sigma(k+1) >= 2*(k+1)-1.at n=9A103289
• Numbers k such that lcm(1,2,3,...,k)/13 equals the denominator of the k-th harmonic number H(k).at n=30A112818
• Totally multiplicative sequence with a(p) = 9p-1 for prime p.at n=41A166658
• Coefficients of expansion polynomial:p(x,t)=Exp[ -t^2* x](1 - t)^(-x)/x.at n=38A174893
• T(n,k) = count of degree k monomials in the elementary symmetric polynomials e(mu,k) summed over all partitions mu of n.at n=24A209669
• Triangle read by rows: T(n,g) = number of general immersions of a circle with n crossings in a surface of arbitrary genus g (the circle is not oriented, the surface is oriented).at n=28A260848
• Even 14-gonal (or tetradecagonal) numbers.at n=34A270704
• Number of integers in n-th generation of tree T(3/2) defined in Comments.at n=27A274152
• Number of terms in the fully expanded n-th derivative of x^(x^x).at n=34A281434
• Numbers k such that both k and k+1 are Zumkeller numbers (A083207).at n=5A328327
• Even composite integers m such that U(m)^2 == 1 (mod m) and V(m) == 7 (mod m), where U(m)=A004187(m) and V(m)=A056854(m) are the m-th generalized Lucas and Pell-Lucas numbers of parameters a=7 and b=1, respectively.at n=42A337782
• Numbers k such that k and k+1 have the same average of unitary divisors.at n=23A349222
• Numbers k such that k and k+1 both have an odd number of abundant divisors.at n=3A381548