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A328451
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Sorted positions of first appearances in A328219, where if n = A000040(i_1) * ... * A000040(i_k), then A328219(n) = LCM(1+i_1,...,1+i_k).
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4
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1, 2, 3, 5, 6, 7, 13, 14, 15, 17, 19, 21, 26, 29, 35, 37, 38, 39, 42, 47, 51, 53, 58, 61, 65, 74, 78, 79, 87, 89, 91, 95, 101, 105, 106, 107, 111, 113, 119, 122, 127, 133, 141, 145, 151, 158, 159, 173, 174, 178, 181, 182, 183, 185, 195, 199, 202, 203, 214, 221
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OFFSET
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1,2
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COMMENTS
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A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.
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LINKS
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EXAMPLE
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The sequence of terms together with their prime indices begins:
1: {}
2: {1}
3: {2}
5: {3}
6: {1,2}
7: {4}
13: {6}
14: {1,4}
15: {2,3}
17: {7}
19: {8}
21: {2,4}
26: {1,6}
29: {10}
35: {3,4}
37: {12}
38: {1,8}
39: {2,6}
42: {1,2,4}
47: {15}
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MATHEMATICA
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dav=Table[If[n==1, 1, LCM@@(PrimePi/@First/@FactorInteger[n]+1)], {n, 100}];
Table[Position[dav, i][[1, 1]], {i, dav//.{A___, x_, B___, x_, C___}:>{A, x, B, C}}]
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PROG
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(PARI)
up_to = 1024;
ordinal_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), pt); for(i=1, length(invec), if(mapisdefined(om, invec[i]), pt = mapget(om, invec[i]), pt = 0); outvec[i] = (1+pt); mapput(om, invec[i], (1+pt))); outvec; };
A003961(n) = my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); \\ From A003961
A290103(n) = lcm(apply(p->primepi(p), factor(n)[, 1]));
vord_trans = ordinal_transform(vector(up_to, n, A328219(n)));
for(n=1, up_to, if(1==vord_trans[n], print1(n, ", "))); \\ Antti Karttunen, Oct 18 2019
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CROSSREFS
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Sorted positions of first appearances in A328219.
The GCD of the prime indices of n, all plus 1, is A328169(n).
The LCM of the prime indices of n, all minus 1, is A328456(n).
Partitions whose parts plus 1 are relatively prime are A318980.
Numbers whose prime indices plus 1 are relatively prime are A318981.
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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