524224

Appears in sequences

• a(n) is the number of distinct patterns (modulo geometric D3-operations) with strict median-reflective (palindrome) symmetry (i.e., having no other symmetry) which can be formed by an equilateral triangular arrangement of closely packed black and white cells satisfying the local matching rule of Pascal's triangle modulo 2, where n is the number of cells in each edge of the arrangement. The matching rule is such that any elementary top-down triangle of three neighboring cells in the arrangement contains either one or three white cells.at n=37A060549
• a(n) = 10*a(n-2) - 16*a(n-4) for n > 3, a(0) = 1, a(1) = 5, a(2) = 14, a(3) = 34.at n=12A083332
• Divisors of perfect numbers (A000396), sorted.at n=44A096360
• Let S(n)=Sigma(n)/2. Numbers n such that S(S(n))=n, 1/2-Sociable number of order 1 or 2.at n=28A113791
• Divisors of 33550336, the 5th perfect number.at n=19A133025
• Triangle read by rows: row n lists divisors of n-th perfect number A000396(n).at n=53A133031
• Divisors of 16775168 (half the 5th perfect number).at n=18A138815
• Triangle read by rows: row n lists the proper divisors of n-th perfect number A000396(n).at n=49A139246
• Triangle read by rows: row n lists the divisors of n-th perfect number A000396(n) that are multiples of n-th Mersenne prime A000668(n).at n=23A139247
• Numbers whose binary representation is the concatenation of 2n-1 digits 1 and n-1 digits 0.at n=6A147590
• a(n) = 64*(2^n - 1).at n=13A175166
• Numbers n such that 8^9 + n^2 is a square.at n=6A180972
• Largest members of fully k-sociable cycles of order r.at n=25A183023
• Non-unitary amicable numbers.at n=25A259037
• Larger of a non-unitary amicable pair.at n=12A259039
• Numerators of the positive solution to 2^(n-1) = Sum_{d|n} a(d) * a(n/d).at n=20A299151
• Nonunitary superperfect numbers: numbers k such that nusigma(nusigma(k)) = k, where nusigma(k) = sigma(k) - usigma(k) is the sum of nonunitary divisors of k (A048146).at n=29A329884
• Number of compositions of n that are not strictly increasing.at n=20A337698
• Numbers that are either already perfect, or a perfect number is eventually reached if we start doubling them.at n=25A341622
• Greater member of Carmichael's variant of amicable pair: numbers k < m such that s(k) = m and s(m) = k, where s(k) = A371418(k).at n=12A371420