19559

Properties

Appears in sequences

• a(1) = 1, a(n) = Sum_{k=1..n-1} Sum_{d|k} a(d).at n=14A014668
• Primes which can be expressed as sum of distinct powers of 7.at n=3A077721
• Primes p such that 2*p+1 and ((2*p+1)^2 + 1)/2 = p^2 + (p+1)^2 are primes.at n=23A098717
• Indices of primes in sequence defined by A(0) = 63, A(n) = 10*A(n-1) + 43 for n > 0.at n=6A101535
• Primes p that divide Fibonacci[(p-1)/7].at n=26A125253
• Primes congruent to 30 mod 59.at n=39A142757
• Primes congruent to 39 mod 61.at n=33A142837
• Primes of the form : 2*p+1=p1(prime), 2*p1+3=p2(prime), 2*p2+5=p3(prime).at n=37A143912
• Primes congruent to 34 mod 71.at n=30A154624
• Number of ordered triples (w,x,y) with all terms in {-n,...-1,1,...,n} and w+5x+5y>0.at n=17A211627
• Principal diagonal of the convolution array A213566.at n=9A213567
• Primes whose base-7 representation also is the base-2 representation of a prime.at n=3A235464
• Primes p such that p^4 + p + 1 and p^4 - p - 1 are also prime.at n=14A236073
• Conjecturally, the largest k such that prime(n)^2 is the largest squared prime divisor of binomial(2k,k).at n=38A239623
• Primes p = prime(n): such that p.n and n.p both are prime, where (.) indicates concatenation.at n=30A243886
• Primes p such that A001175(p) = (p-1)/7.at n=15A308792
• Primes p such that A001177(p) = (p-1)/7.at n=8A308800
• a(n) is the number of solutions when placing the numbers 1..n in an n X n square according to the rules in the Comments section.at n=19A329094
• Number of pairs of two disjoint sets of n positive integers with product A354457(n).at n=13A372794
• Primes having only {1, 5, 9} as digits.at n=35A385781