27639

Appears in sequences

• Numbers k such that sigma(k) = phi(k+1) + phi(k) + phi(k-1).at n=16A065986
• a(n) is the square of the n-th partial sum minus the n-th partial sum of the squares, divided by a(n-1), for all n>=1, starting with a(0)=1, a(1)=5.at n=13A087958
• Integers N such that by inserting + or - or * or / or ^ between each of their digits, without any grouping parentheses, you can get N (the ambiguous a^b^c is avoided).at n=15A156954
• Integers n such that by inserting between their digits + or - or * or / or ^ or nothing (i.e., concatenate two digits) you recover n back in a nontrivial way.at n=20A157198
• Odd numbers n such that the sum of the binary digits of n and n^2 both equal 12.at n=31A261593
• Number of 5 X n binary arrays with rows and columns lexicographically nondecreasing and column sums nonincreasing.at n=8A266472
• Number of nX4 0..1 arrays with every element equal to 1, 2, 3, 5, 6 or 8 king-move adjacent elements, with upper left element zero.at n=5A299461
• Number of nX6 0..1 arrays with every element equal to 1, 2, 3, 5, 6 or 8 king-move adjacent elements, with upper left element zero.at n=3A299463
• T(n,k)=Number of nXk 0..1 arrays with every element equal to 1, 2, 3, 5, 6 or 8 king-move adjacent elements, with upper left element zero.at n=39A299465
• T(n,k)=Number of nXk 0..1 arrays with every element equal to 1, 2, 3, 5, 6 or 8 king-move adjacent elements, with upper left element zero.at n=41A299465
• Near 2-hyperperfect numbers: numbers k such that sigma(k) - 3*k/2 - 1/2 is a proper divisor of k.at n=14A305616
• Numbers that can be represented using their digits in the order of appearance, the operations +, -, *, /, ^, and any parentheses.at n=42A386936