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A294897 a(n) = Product_{d|n, gcd(d,n/d)>1} prime(A101296(gcd(d,n/d))-1). 6

%I #9 Nov 21 2017 21:36:10

%S 1,1,1,2,1,1,1,4,2,1,1,4,1,1,1,12,1,4,1,4,1,1,1,16,2,1,4,4,1,1,1,36,1,

%T 1,1,80,1,1,1,16,1,1,1,4,4,1,1,144,2,4,1,4,1,16,1,16,1,1,1,16,1,1,4,

%U 252,1,1,1,4,1,1,1,1600,1,1,4,4,1,1,1,144,12,1,1,16,1,1,1,16,1,16,1,4,1,1,1,1296,1,4,4,80,1,1,1,16,1

%N a(n) = Product_{d|n, gcd(d,n/d)>1} prime(A101296(gcd(d,n/d))-1).

%H Antti Karttunen, <a href="/A294897/b294897.txt">Table of n, a(n) for n = 1..16384</a>

%H <a href="/index/Eu#epf">Index entries for sequences computed from exponents in factorization of n</a>

%F a(n) = Product_{d|n} A008578(A101296(gcd(d,n/d))).

%F For n >= 1, A001222(a(n)) = A048105(n).

%o (PARI)

%o up_to = 16384

%o rgs_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(om,invec[i]), my(pp = mapget(om, invec[i])); outvec[i] = outvec[pp] , mapput(om,invec[i],i); outvec[i] = u; u++ )); outvec; };

%o A046523(n) = { my(f=vecsort(factor(n)[, 2], , 4), p); prod(i=1, #f, (p=nextprime(p+1))^f[i]); }; \\ This function from _Charles R Greathouse IV_, Aug 17 2011

%o v101296 = rgs_transform(vector(up_to, n, A046523(n)));

%o A101296(n) = v101296[n];

%o A294897(n) = { my(m=1); fordiv(n,d,if(gcd(d,n/d)>1, m *= prime(A101296(gcd(d,n/d))-1))); m; };

%Y Cf. A005117 (the positions of ones).

%Y Cf. A101296, A294895.

%Y Cf. also A292258 (A292259), A293515, A294875 for similar filter sequences.

%K nonn

%O 1,4

%A _Antti Karttunen_, Nov 21 2017

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Last modified April 25 12:53 EDT 2024. Contains 371969 sequences. (Running on oeis4.)